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Thread: Help needed ASAP

  1. #1
    Registered User Jeff G 78's Avatar
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    Default Help needed ASAP

    I am at my wit's end and need help on my 260Z race car. Ever since I got the car two years ago, I have had issues at high RPM and after trying lots of things, I'm pleading for help. Here's the engine background...

    • L26 engine just rebuilt with new rings, valve job, and a mild cam
    • Thermostat guts removed leaving only the ring and cage for a restriction
    • Prior to rebuild a few weeks ago, it was 100% original
    • 3 screw SU's with SM needles, floats set to spec and chokes working smoothly and carbs synchronized. N36 intake
    • Previously used OE needles in carbs
    • New mechanical fuel pump with 260Z electric pump removed
    • Previously tried another new mechanical pump and an electric pump as well
    • Stock exhaust manifold with a 2-1/4" straight pipe and a single glass pack up front
    • Clean '75 fuel tank with new filters
    • Previously ran a POR-15 lined '74 tank with new filters
    • ZX distributor with E12-80 module. 10BTDC at 800 RPM and 37 total advance at 2500 RPM
    • Previously ran stock magnetic pickup distributor




    So, the car starts right up and idles like a champ. It free revs cleanly and runs well at low RPM. On the track (car is not street legal, so all testing done on road courses), the exhaust note goes totally flat at about 5000 RPM and the car won't rev any higher. It makes no power at that point. Sometimes, the RPM limit before it goes flat is much lower than 5k. It's slightly better at part throttle, high RPM that at WOT, but the problem is still there. It doesn't always happen though. Some days, it runs fine for a short or even extended length of time and other days, it runs poorly right off the trailer. It happens at all temperatures and weather conditions.

    In the past, we had some success pinching off the fuel return line, but yesterday that didn't help at all. I tried moving the needles up slightly to richen it up and the problem got worse. We ran out of time to try moving them the other way. In the past, we have tried running with no air filter, we also tried running it with the hood off. We have the fuel rail thermal wrapped and we have extra heat shielding between the intake and exhaust manifolds. Nothing helps at all.

    The issue is exactly the same pre and post engine rebuild, pre and post fuel tank swap, pre and post distributor swap, pre and post fuel pump swap, and pre and post stock to SM needle swap.

    We have a 25+ hour endurance race in 12 days and we are out of ideas. Does anybody have a clue what's going on?

    EDIT: One thing I just thought of is that the temp gauge doesn't work (reads ~130) even though I have swapped in another used sensor and tried a different gauge. The engine and radiator get hot to the touch like they should, but is there any chance it's running too cold?
    Last edited by Jeff G 78; 09-26-2011 at 07:51 AM. Reason: Added info
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
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    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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  2. #2
    Boat Anchor Repairman Captain Obvious's Avatar
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    Hi Jeff,

    I'm sure you know already... "It could be lots and lots and lots of things", right? But from what you've described, I would guess fuel delivery issues. Sounds like you're getting enough fuel under all conditions except at high RPM full throttle conditions when, of course, you need the most of it. Only thing that seems to contradict that is this part:

    Some days, it runs fine for a short or even extended length of time and other days, it runs poorly right off the trailer. It happens at all temperatures and weather conditions.

    In the past, we had some success pinching off the fuel return line, but yesterday that didn't help at all. I tried moving the needles up slightly to richen it up and the problem got worse.
    Could you put a pressure gauge on the fuel rail so that you can see it as you drive, and take a run with it installed?

    Have you checked to make sure that the inlet filter screens in your SU's are clean? You might also pull the needle valves and make sure crud isn't partially plugging them too. I've seen paper towel fibers get through the fuel lines and gather like a wood pulp wad in the needle valve. They built up gradually and can act intermittent.

    As an aside... Wow! I'm surprised you don't have fifty responses with help by this point. I would have expected a post like yours to draw in all the experts from world around!

  3. #3
    Registered User cozye's Avatar
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    Yeah, sounds like fuel delivery issue to me as well.
    1978 280z 4sp

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    Registered User Jeff G 78's Avatar
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    Quote Originally Posted by Captain Obvious View Post
    Hi Jeff,
    As an aside... Wow! I'm surprised you don't have fifty responses with help by this point. I would have expected a post like yours to draw in all the experts from world around!
    Thanks for the help Captain! Yeah, I thought I'd get lots of responses too, but I guess I just didn't catch the expert's attention. Maybe next time I'll ask what the biggest tires I can run or if anybody has ever tried a turbo on a Z.

    I have taken the carbs apart many times to check the inlet screens and float valves and they are always clear. Last night, I talked to a British car mechanic and he too thinks it's a problem getting fuel to the carbs, not the tuning or carbs themselves. He suggested ditching the mechanical pump and the return line and installing an electric pump and pressure gauge. We already tried that, but maybe the electric pump we bought was a dud. Who knows...

    I also talked to a Z guy from Atlanta who races and he just went through exactly the same issue last weekend on his L28 powered 510. He solved the problem with an electric pump. He told me that the new metal bodied fuel pumps don't flow as much fuel as the old cast bodied pumps. I have never heard that, but I guess it could be true. SOMETHING is obviously wrong and it might just be that the pump can't keep up.

    He said one other thing that he said that made sense. I told him I tried to slide the needle up a bit to richen the mixture and the car ran even worse, cutting out at 4k rather than 5k. He said that with a richer mixture, I'm draining the bowls even faster which is why it cut out sooner. I was thinking that it was too rich at that point, but his theory sounds plausible.

    I plan to bypass the mechanical pump and install a new electric pump and gauge as well as block off the return line. The British mechanic will take a look at the car as well and give the carbs an expert tune.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
    https://www.facebook.com/Jeff.Grauer

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    But you are saying it falls over as soon as you hit 5 grand right? Doesn't seem to me you'd drain the floatbowls in that short a period of time. Steve had a starvetion problem on the E-prod car but it was at the end of a mile and a half front straight at wide open pulling hard throttle. The second he let off for the turn, the fuel pump caught back up and no more issue until the next lap.

    If you'd like to talk to him call me and I'll give you the number at the shop. 503-587-9800
    Bruce Palmer
    Salem Or
    Sales@ztherapy.com
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    503-587-9800

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    Registered User Jeff G 78's Avatar
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    Thanks Bruce, I'll call you after work today before you leave.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
    https://www.facebook.com/Jeff.Grauer

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    Registered User Jeff G 78's Avatar
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    Hey Bruce, I just asked my teammate (I never drove the car on Sunday) if the car accelerated OK when he first pulled onto the track and he said no. His run in the car was after I raised the needles a bit to see if that made any difference. The car wouldn't rev above 4k for him even right out of the pits after it idled for a bit. I should get more feedback from the other two who drove the car prior to me adjusting the needles.

    I did not check the bowls on Sunday, so I guess it's possible there could be some debris in the valves, but there never has been anything there in the past. We run a filter near the tank and another before the mechanical pump. Both filters are 3/4 full of fuel when we check them in the pits, but I don't know what they look like on the track at speed.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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    Registered User Jeff G 78's Avatar
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    Bruce, I have a quick question. What is the ID of the fuel hoses between the bowls and chokes? I need to buy some clear hose at lunch today to double check the fuel height in the bowls.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
    https://www.facebook.com/Jeff.Grauer

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    Registered User Jeff G 78's Avatar
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    Update: I got feedback from another driver and she said that when she drove the car (prior to my needle test), the car ran fine for the first few laps and then wouldn't rev past 5k. After her session, I raised the needles and re-balanced the carbs and it was the next driver who reported the issue occurring right away and at 4k rather than 5k.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
    https://www.facebook.com/Jeff.Grauer

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    Registered User Randalla's Avatar
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    This is a long shot, but Duffman, on this site, was having a similar problem with his L-28 with mechanical fuel pump and a fuel pressure gauge installed inline between the fuel rail and the SU carbs. We went though many of the same things you did with no success. We set and re-set floats, checked for obstructions in fuel delivery, rebuilt the distributor, etc. The fuel pressure gauge fluctuated periodically, indicating an air suction issue somewhere. That led us to look more closely at fuel delivery from the tank to the carbs. The fuel tank had been out of the car recently which was a further clue. What Duffman discovered was the short fuel hose from the tank to the metal fuel line was sucking air where the clamps were. The car never leaked fuel but was apparently sucking in air and creating a lean condition under hard acceleration. As soon as the hose was replaced (some cracks were seen around the end) the problem was gone. Before you lose the mechanical fuel pump, install an inline fuel pressure gauge and watch the pressure under all conditions from idle to WOT. If you notice a 20-25% change you may also be sucking air somewhere. By the way Jeff, I am an ex-Detroiter, moving from Milford, MI to Scottsdale, AZ in 1994. Used to head to the Northville Dairy for ice cream when I was a kid.
    Last edited by Randalla; 09-27-2011 at 10:26 AM.

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    I wouldn't rule out ignition problems yet, especially if the fuel pressure isn't wandering around. The 240 distributors had shaft bearings fail quite a bit. Not sure about your ZX dizzy. A bad electrical connection, coil, ignition wires, plugs, dizzy bearing problem could take your top end out.

    I'd do a compression test as well just in case something got missed during your engine rebuild. Improperly installed timing chain or broken chain tensioner will also do that to you. Hopefully you put in a new chain during your rebuild.
    Lee - 2/72 240Z

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    Registered User Travel'n Man's Avatar
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    Just my two cents worth:

    100 micron filter coming out of the tank (or stronger for racing - one the size of an oil filter would be best) to Electric fuel pump to Fuel Pressure regulator to 20 micron fuel filter to fuel line. Sounds like a pressure of fuel supply could be running short with the mech pump - I belive I have read that the mech pump can only supply 2.5 lbs of pressure. Sounds like you need a little more - keep us posted.

    What pressure setting do you have on your electric fuel pump? - I would take it to at least 3.5 to 4 psi and give that a shot (monitor your carbs while you are reviewing - I would hate for your to force out fuel of your SU's on to your hot header - fire safety equipment is a must at this point!
    Life's a journey; enjoy the ride!

    Mitchell
    L28 - N42 Block w/Flat tops - N42 Rebello Head & Cam - Triple 40 PHH Mikuni's - Headers - Recaro Seats -
    R180 3.9 Diff - Close Ratio 5 Speed - Toyota Vented Brake Upgrade w/ Porterfield High Performance Pads & Shoes

    1972 Datsun 240z
    HLS30-75040


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    Over on the 510 forum there is a saying..... If you think it's fuel, it's electrical and if you think it's electrical, it's fuel........

    Oh, and a question if I may..... Why do the needles get adjusted up and down rather than the nozzle which is all about adjustment? I don't think this is the first time I've heard of this being done on here. Needles move an RCH where the nozzles adjust a half mile up and down so to speak.
    Bruce Palmer
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    Registered User Jeff G 78's Avatar
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    Quote Originally Posted by Bruce Palmer View Post
    Over on the 510 forum there is a saying..... If you think it's fuel, it's electrical and if you think it's electrical, it's fuel........

    Oh, and a question if I may..... Why do the needles get adjusted up and down rather than the nozzle which is all about adjustment? I don't think this is the first time I've heard of this being done on here. Needles move an RCH where the nozzles adjust a half mile up and down so to speak.
    Bruce, the needle adjustment was a trackside test just to see what it would do. I didn't really expect it to fix anything, but I wanted to see what direction it took us.

    As for electrical vs. fuel, I certainly agree, but I have tried three different distributors and three different coils. In every combination, the symptoms didn't change at all. I will add another ground strap, but I don't think that is a problem either.

    Randalla, I have read about fuel lines sucking air elsewhere as well. All of the hoses are new and the hard lines are in good condition, but I will verify once I get a big gauge connected that I can watch. You must be talking about Guernsey Farms Dairy. I live within walking distance of it and go there often in the summer for ice cream.

    What electric pump does everybody recommend? And don't say get an RX7 pump from a JY because I haven't seen a JY RX7 in these parts for decades. I'll probably look for a 3 -4 psi Facet cube pump, but I want to find something local if possible to save time.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
    https://www.facebook.com/Jeff.Grauer

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    Registered User madkaw's Avatar
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    Okay, I'll throw in my thoughts. You haven't said-or I missed -what theplugs look like-carboned, lean??
    Check your float bowl hoses. I bought some from Bruce-sorry Bruce- that collapsed or kinked, which shut off fuel obviously. They could be kinking and unkinking under heat conditions.
    Float bowl adjustments-does the car bog under hard acceleration before it gets to this wall at 5k? If NOT, I would go in there and tweek those floats to maximize fuel. You'll know if you tweeked too much. It could still be running your bowls dry-been there!

    Sorry I was so late on suggestions-I guess i have been sulking in my own misery here lately.
    Last edited by madkaw; 09-27-2011 at 02:24 PM.
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
    3.90 Subaru STI LSD

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    Carter Fuel Pump
    Holley 12-804 Fuel Regulator
    Holley 162-551 Fuel Filter
    Life's a journey; enjoy the ride!

    Mitchell
    L28 - N42 Block w/Flat tops - N42 Rebello Head & Cam - Triple 40 PHH Mikuni's - Headers - Recaro Seats -
    R180 3.9 Diff - Close Ratio 5 Speed - Toyota Vented Brake Upgrade w/ Porterfield High Performance Pads & Shoes

    1972 Datsun 240z
    HLS30-75040


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    Registered User madkaw's Avatar
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    I forgot to ask, why aren't you using a thermostat. I would want one in there to regulate temp. You don't want a cold engine.
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
    3.90 Subaru STI LSD

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    Registered User Jeff G 78's Avatar
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    Quote Originally Posted by madkaw View Post
    I forgot to ask, why aren't you using a thermostat. I would want one in there to regulate temp. You don't want a cold engine.
    The T stat is gutted simply to avoid a stuck thermostat and an overheating condition in race conditions. I can certainly put one back in. That was on my radar as a possible problem, but I figured it wouldn't be an instantaneous cutout, but rather a general running problem.

    As for the plugs, I didn't have a chance to shut the car off during a stumble to check them at that moment, but after a session and cool down lap, the plugs are a perfect light tan color.

    I can't say if it bogged prior to hitting the wall, but I don't believe so. I think it's fine and then terrible.

    I am running new hoses from Bruce. When I installed them, I made sure they were straight and they show no signs of kinking, but how can I tell? Is there any evidence to look for of them collapsing?

    Mitchell, thanks for the pump suggestion, but I need to find something local due to time constraints and the only thing I have found is a Facet 1.5 - 4 psi cube pump from Napa. I just talked to Bruce and he thinks that will work fine. The low end of the pressure range scared me a bit, but ??? They also have a 4 - 7 psi Facet cube pump, but Bruce is worried that the pressure will puke fuel out the vents.

    Thanks all for the help and keep the suggestions coming. IF I ever fix the problem, I'll be sure to report my findings.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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    Just as important as the pump is the fuel pressure regulator - you really need to control that fuel flow! Get Bruce's idea on what PSI should be ran for your application with your engine set up and racing requirements - he would know the best! Most of all - keep that fire extinguisher handy for your first race!
    Life's a journey; enjoy the ride!

    Mitchell
    L28 - N42 Block w/Flat tops - N42 Rebello Head & Cam - Triple 40 PHH Mikuni's - Headers - Recaro Seats -
    R180 3.9 Diff - Close Ratio 5 Speed - Toyota Vented Brake Upgrade w/ Porterfield High Performance Pads & Shoes

    1972 Datsun 240z
    HLS30-75040


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    As far as the hoses, mine were brand new and would kink. I can't quite remember how I discovered this, but I believe I was just checking that the nozzles were flush after closing the choke.
    I would run a quality thermostat-IMHO

    The point i was making about the bogging is that even if the float bowls were lean, you would probably see decent acceleration until they emptied out. If they were lean you would definitely hit that wall after at WOT for a while. Mine are adjusted beyond factory specs.

    It would be nice if you had a wideband to see what the mixture is doing. I had SM needles in my Z and took them out and put OEM back in. The OE needles supplied enough for my mods.
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
    3.90 Subaru STI LSD

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    Registered User black gold man's Avatar
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    Hi jeff I believe i have a ome 83 rx7 carb fuel pump around somewhere .
    Let me know if you want it i will look for it.
    Only 70,000 mi on it.
    Bill

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    I had the problem with new hoses on my carbs as well. I went back to the old ones which were more rigid.

    Do you have a spare set of carbs that you could swap in just for sh#Ts & grins? That could at least remove one variable.

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    I don't have a clue about the stress of racing but...

    Maybe you've got two problems going on. I understand your not wanting a stuck thermostat to toast your engine, but seriously, even with a malfunctioning gauge, if the thermostat stuck, I think you'd pit because the engine would start running badly before any great damage occurred. If the engine is too cold, and you've tuned the carbs for the cold running engine -- wait, I just read a thread on the effect of temperature and altitude on carb tuning. Running 50 -- 60 degrees below normal might not have a one to one correspondence with the effect of air temperature on mixture, but surely it must have some effect, would 1:2 be an unreasonable guess? That would give you an unusually dense air-fuel mixture.

    Combine that with your first post describing the effect of RPMs on the engine, which sounds very similar to my experiences when I adjusted (another word, beginning with "f" might better describe the entire process of my first attempt) float levels. My first attempt had fuel running out the air cleaner. I decided that lowering the float bowl level was appropriate. Car would run fine around town, even accelerate normally up to and cruise at 70 mph. But run it through the gears hard and fast, hack, ack, ack or drop into 4th and run it from 70 (~3600 rpm) it would make it to about 95, then start hacking and be unable to hold speed. Might not be the bowl levels, but I'm thinking an unusually heavy fuel demand caused by low engine temp and some sort of fuel delivery problem might well be the problem.

    My not even two cents.

    Chris

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    Registered User Randalla's Avatar
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    One more long shot, but worth considering. Do you notice any difference when the gas tank is topped off vs. 1/2 tank or less? If so you may want to check the fuel pick up tube in the tank. I don't know if this has actually happened or not but it was something we looked at on Duffman's car since he had recently had the tank boiled out and we suspected the chemicals may have perforated the tube, thereby allowing air to be sucked into the system. Admittedly this is a real long shot. You know of course, that when you find out what's causing all your problems it will be some little detail we have all missed so far.

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    I think you need to come up with somekind of temp guage
    Last edited by madkaw; 09-27-2011 at 03:57 PM.
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
    3.90 Subaru STI LSD

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    Registered User Jeff G 78's Avatar
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    OK, thanks all. I will add a (quality) thermostat back in and see if the temp gauge actually does work.

    Bill, YES, please try to find the pump and let me know if you find it. I will be buying a pump tomorrow after work if you don't find it.

    Randalla, no, the tank is good and we ran it with 4, 12 and 16 gallons of gas in that order with no change.

    Steve, I agree that a wide band work be the best way, but we just don't have time to add one in time. We are thinking about going to a dyno this weekend (if we can get in) though to check and tune. I might also try the OE needles, but we did have the problem with and without the SM needles.

    No other carbs available and no old hoses to try. I think the old hoses cracked when I removed them.

    Gotta run and go pick up the Z from a race shop an hour away, but thanks all!
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
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    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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    Well atleast look at the hoses and see if they have a tendacy to kink when moving the nozzle. It should be easily apparent if they tend to kink
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
    3.90 Subaru STI LSD

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    We had similar symptoms on our 240Z. Ran great up to 5K RPM then went away, popping and not making power. It turned out to be floating points due to the wrong points cam. I know you do not have points, but the symptoms you report are to close to our experience to let it go by. Is your timing stable at high RPM?

    Fuel pump - We are using a Holley "Red" fuel pump mounted in the rear where the original electric pump was. The mechanical pump has been removed. The Holley is rated for 71 GPH which should be more than enough for your mod level. You will need to use an in-line pressure regulator. We are using one of those little, round type (see image below) with good results but I suspect it might not flow enough fuel for higher power levels.

    You mentioned you have 2 fuel filters before the pump. Perhaps there is too much resistance on the suction side of the pump as a result. Have you tried it with only 1 filter?

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    Are you sure the fuel pickup in the tank is not pinched or has POR-15 partially blocking it?
    Just another wild idea.

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    madkaw, I will look closely at the hoses, thanks.

    beermanpete, I thought about the dual filters, but have never tried to run just one. I haven't looked at the timing at high rpm, but it's dead stable at 2500 where I checked the total advance. I'll check at higher rpm too. I ran a holley red and a regulator just like that on a '72 with triple Webers. I called around and can't find anything local. I do like the idea of higher pressure and flow with a regulator adjusting it back down to the exact pressure needed.

    pizzaman, this tank hasn't been treated. The first tank was and yes, the inlet was clogged with POR. That was one of the reasons for the tank swap. This tank is clean and free flowing.
    Jeff
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    Hi Jeff,

    Of course, armchair troubleshooting is fraught with potential incorrect diagnoses, but from your description, I agree with the assessment that it's a problem getting fuel TO the carbs, not a problem inside the carbs themselves. Have to start with the simple stuff like filter screens though, right?

    So next? A fuel pressure gauge between the pump and the carbs is a must at this point. And I wouldn't block off the return to the tank until you know what the pressure is. You don't want to overwhelm your float valves and blow fuel out the overflow tubes especially if you put an electrical pump in series with the mechanical.

    You should be able to test the "sucking air" theories by running without a gas cap. I haven't completely digested the original tank venting system details, but I believe the original system is "supposed" to run at a slight vacuum. That vacuum is controlled at the stock filler cap. No filler cap - No possible vacuum - No pressure differential - No sucking air. (Of course, unless you're creating a pressure drop elsewhere with a clogged filter or something.) Just remember on left handers that you've got no filler cap.

    The ID of the tube between the float bowl and carb bodies is 3/16 ID. If you want to do more than check the bowl levels and actually run the car with some clear stuff, I would recommend the gasoline grade F-4040-A Tygon. http://www.tygon.com/tygon-f4040a-tubing.aspx. How about some Tygon between the float bowl and the carb body and an engine bay cell phone video cam taped to the fender well? If you see bubbles coming through that tube, you're sucking the bowls dry. At least you'd have the "what?". All you would need to do is the "why?".

    I don't have any Tygon, but I do have a plenty of suitable Buna-N black opaque 3/16 ID tubing if you need some. If you're worried about kinking or collapsing at the bend, you could probably put on a length longer than usual and include a strain relief loop. PM me if you want to talk about it.

    As an aside... 29 replies in 300 views. Now that's what I'm talkin bout! Glad I could break the ice.

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    Jeff - When I purchased my head from Dave Rebello (along with engine rebuild parts and pieces) he instructed me to set my timing with high RPM @ 3500 - you may want to do that just to get all you can get out of your timing advance - I'm sure if you do a search you would get a lot of info and benefits from the different settings - it's all going to depend on your engine - cam - and head for your final setting though.
    Life's a journey; enjoy the ride!

    Mitchell
    L28 - N42 Block w/Flat tops - N42 Rebello Head & Cam - Triple 40 PHH Mikuni's - Headers - Recaro Seats -
    R180 3.9 Diff - Close Ratio 5 Speed - Toyota Vented Brake Upgrade w/ Porterfield High Performance Pads & Shoes

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    Jeff,

    One more long shot....(don't laugh), it could be the *Alternator*. Seriously.

    On my 78 280z I found I could only rev to about 2000 rpm then it would die until the revs dropped a bit.

    My memory of the trouble shooting is dim as it was 18-20 years ago, but I remember my first clue was when I happen to see the voltage on the dash gauge would drop steeply when the engine cut out. As I recall, disconnecting the alt belt made it much worse to my surprise. Disconnecting all the wires to the alternator made the problem go away.

    I eventually opened the alternator up and found a wire on the rotor going to the commutator had a break in the insulation as it crossed very closely over something else. I surmised that at a certain RPM the voltage being generated would arc across the small gap. I unsoldered it and slipped on an insulating sleeve from a set of replacement brushes, then reassembled. It worked great for many, many years. I still have the alternator (and engine) stored away.

    So yes, it is a long shot, but since you are desperate, and this is cheap and easy to try, I suggest you give this a shot. Disconnect (and insulate) *all* the alternator wires and see if it runs.

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    Quote Originally Posted by Travel'n Man View Post
    Just my two cents worth:

    100 micron filter coming out of the tank (or stronger for racing - one the size of an oil filter would be best) to Electric fuel pump to Fuel Pressure regulator to 20 micron fuel filter to fuel line. Sounds like a pressure of fuel supply could be running short with the mech pump - I belive I have read that the mech pump can only supply 2.5 lbs of pressure. Sounds like you need a little more - keep us posted.

    What pressure setting do you have on your electric fuel pump? - I would take it to at least 3.5 to 4 psi and give that a shot (monitor your carbs while you are reviewing - I would hate for your to force out fuel of your SU's on to your hot header - fire safety equipment is a must at this point!
    I have to agree it makes since that you are running out of fuel under hard load. That would also explain the effect of raising the needles and increasing the instances and decreasing the RPM of occurrence. You have changed all other cause effect items (electrics, overhaul, etc...) Focus on fuel system-supply.
    Jerry Purcell
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    Thanks all for the continued ideas. I got the car back late last night and I'll start trying all of the great suggestions you have given me. My plan is to do all of the most likely fixes. From there, I'll prepare to do others at the track in case the not-so-likely becomes the likely once I hit the track. I have one week to get the parts needed and installed before I leave for my race.

    Here's my game plan:

    • Remove the mechanical pump and install an electric pump near the tank with a single quality filter.
    • Install a fuel pressure gauge and position it to be in view from the driver's seat for testing.
    • Check all fuel lines and hoses for possible leak paths.
    • Check carb hoses for signs of kinking.
    • Recheck carb inlet screens and float valves for debris
    • Install a new quality thermostat.
    • Recheck the valve clearances.
    • Perform vacuum, compression, and leakdown tests on engine.
    • Install an additional ground strap between the engine and body.
    • Check fuel pressure w/return.
    • Block fuel return system.
    • Recheck fuel pressure w/o return.
    • Set the SM needles back to the properl height.
    • Retune/synchronize carbs.
    • Adjust the fuel level in the bowls per Bruce's method. (set fuel level to 1/16" below top of nozzles)
    • Check timing at high RPM.




    If nothing jumps out as a smoking gun, I will *try* to get to a dyno this weekend. More than likely, I will not have the time, so we will leave a day early and pay for the Friday track day at Nelson Ledges to test the changes.

    Assuming it runs well without hitting the 5,000 RPM wall, I will remove the excess fuel line and reposition the fuel pressure gauge to underhood.

    If it still falls on its face and none of the other ideas help, I will swear and pout for a bit and then have a really crappy weekend playing rolling chicane for 25.5 hours.

    Am I missing any of the ideas?

    Hey BGM, did you locate the RX7 pump? If not, I'll buy the facet pump tonight.
    Last edited by Jeff G 78; 09-28-2011 at 02:12 PM. Reason: Added info
    Jeff
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    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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    Since you're looking for WAGs, how about the E12-80 module. From what I've read, and experienced, the electronic ignition modules seem to show different signs when they fail, but they all seem to have high RPM in common as a mode to bring on the failure signs.

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    I'll add it to the list Zed Head. Maybe Geezer will loan me his module so I can try it if needed.
    Jeff
    Northville, Michigan
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    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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    Quote Originally Posted by Jeff G 78 View Post
    I'll add it to the list Zed Head. Maybe Geezer will loan me his module so I can try it if needed.
    Anytime Jeff. I've been really preoccupied as of late but will be glad to help if I can. Just let me know what you need. My dizzy and E12-80 module are known to be working well.

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    How have you been Ron? I hope you've had so time to work on the Z. I'd love to borrow your module. My dizzy is working great and hopefully the module is as well, but it would be nice to rule them out just in case.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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    Jeff-
    Remember that you will need a block off plate for that mech fuel pump - they are still out there if you order one from your local Nissan dealer. Once you get your dyno numbers let me know what they are and let me know the type of dyno your car is getting dyno'd on. I just had mine dyno'd earlier this month - not any crazy numbers due to not jazzing up my cam to a higher stage number but all is good. I've got all the power and torque I could want for my needs.

    Sounds like your fuel delivery system is going to be great - be sure to get your best filter closest to the tank! i did put an in-expensive glass one between the fuel pressure regulator and the fuel rail. My fuel pressure gauge is in my engine bay - be careful where you mount that since you do have live fuel running through it.

    Safety fire extinguishers are a must for any racer at any level - IMO
    Life's a journey; enjoy the ride!

    Mitchell
    L28 - N42 Block w/Flat tops - N42 Rebello Head & Cam - Triple 40 PHH Mikuni's - Headers - Recaro Seats -
    R180 3.9 Diff - Close Ratio 5 Speed - Toyota Vented Brake Upgrade w/ Porterfield High Performance Pads & Shoes

    1972 Datsun 240z
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    That sounds like a great plan. I sure hope you find the issue!!

    Couple of quick comments before it's too late...

    Why are you going to remove the mechanical pump? The 260 originally had an electrical pump in back feeding the mechanical pump up front. And, just because you're not using it, doesn't mean that the pump has to come off the side of the block, right?. You could leave it in place and plumb around it. You could even get fancy and pipe the outlet back to the inlet!

    But if/when you do remove the mechanical pump, you should be able to easily fashion a block off plate out of some sheet steel or aluminum. There isn't anything complicated about the shape. Flat works fine. Cut to rough shape, drill two holes, cut some gasket material, smear some goop, and you're done. I'd hate to see you spend out of your $500 for something like that!

    And... If you're going to put a thermostat in, you should probably have a working temp gauge.

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    I do have a block off plate on a spare 280 head, so I'm good there. I might leave the mechanical pump in place for now though until I get an idea of what's going on.

    As for the temp gauge, I'll have to diagnose it if it still doesn't work. The sensor and gauge came from a '75 that I parted out. The gauge worked 20 years ago when I quit driving it. :-)

    Oh yeah, we always have an extinguisher in the car and ready to use.
    Jeff
    Northville, Michigan
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    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
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    Cool.

    So... What happens if all the investigation into fuel delivery doesn't turn up the problem? How can you tell if the fault is actually ignition, and not fuel delivery? Other than shotgunning it and replacing modules to see if that makes any difference, is there any other diagnostic work ahead of time that can be done?

    I've done no work with the Z ignition to date, other than plugs, wires, caps, etc... maintenance stuff. Thankfully, I've never had to do any diagnostic work, and consider myself blissfully ignorant.

    Maybe the spark is timed correctly, but doesn't have the strength to fire through the densest gasoline cloud that occurs under your problem conditions. You wouldn't see it under light load conditions. Could rev fine all the way to redline while sitting still, but might not work so well once on the track and you're pulling all that fuel and air into it?

    I'm not trying to be pessimistic... Just thinking about contingencies now because once you're at the track, it's all willy-nilly fire drill, right?

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    So are you going to change around pumps before rechecking or richening the floats?
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
    3.90 Subaru STI LSD

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    Steve, My plan is to return the needles to the correct heights first since that's the way we ran it Sunday prior to my experimenting. I will then CHECK the fuel height in the nozzles. If they are WAY off, I might have found a cause, but I doubt they will be off by much. I made myself a float height gauge block last year and that's how I set the levels. My SU's are from a '72 so they have different float heights front to back.

    Here is the block I made per the FSM. It makes setting and checking the floats WAY easier.


    Captain, Unfortunately, it will be fire drill time at the track, but with the right planning, I will have a pile of parts to try and a specific order in which to try them. If NOTHING fixes the problem, then we simply become a rolling chicane for 25.5 hours and I will be very bummed.

    BTW, we have also tried different wires, cap/rotor, and plugs. The spark we have is very strong. When we did a compression check and I pulled the coil wire, the spark was jumping well over an inch from the coil wire to the body.
    Jeff
    Northville, Michigan
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    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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    I never heard back from Black Gold Man on the RX7 pump, so I stopped today at Napa and bought both Facet pumps. I am still confused about which one is the better choice. From what I understand, the SU's want 3 - 4 psi right? The Facet pumps are 1.5 - 4 psi and 4 - 7 psi. The higher pressure pump flows about 10% more as well. So what exactly does a pump's range mean? Is the 1.5 - 4 pump going to be too low of pressure?

    I tried but failed to find a regulator locally, but I got a lead from the guy at Napa of a race shop in town that might have them. I'll check tomorrow. If I find a regulator, the higher pressure Facet pump should be better and then I can adjust the pressure down, but if I don't find anything, which should I use?
    Jeff
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    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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    Quote Originally Posted by Bruce Palmer View Post

    If you'd like to talk to him call me and I'll give you the number at the shop. 503-587-9800
    Jeff -
    I believe Bruce would know exactly what to set that pressure at - my Mikuni's are set at 3.5 psi. Pressure regulator is a must in my opinion. Best of luck. Let us know on that dyno once you get it finalized.
    Life's a journey; enjoy the ride!

    Mitchell
    L28 - N42 Block w/Flat tops - N42 Rebello Head & Cam - Triple 40 PHH Mikuni's - Headers - Recaro Seats -
    R180 3.9 Diff - Close Ratio 5 Speed - Toyota Vented Brake Upgrade w/ Porterfield High Performance Pads & Shoes

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    Don't you hate ambiguous specs. I did a little digging and came away more confused than when I started. I don't know for sure what those numbers mean...

    What are the part numbers for the pumps you bought?

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    Quote Originally Posted by Captain Obvious View Post
    Don't you hate ambiguous specs. I did a little digging and came away more confused than when I started. I don't know for sure what those numbers mean...

    What are the part numbers for the pumps you bought?
    The two Facet pump numbers are 610-1077 and 610-1078. They are Facet pumps, but also have Napa branding on them.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
    https://www.facebook.com/Jeff.Grauer

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    Quote Originally Posted by Travel'n Man View Post
    Jeff -
    I believe Bruce would know exactly what to set that pressure at - my Mikuni's are set at 3.5 psi. Pressure regulator is a must in my opinion. Best of luck. Let us know on that dyno once you get it finalized.
    Bruce suggested I talk to Steve in the shop, but nobody has been answering the shop number when I call. I'll try again tomorrow.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
    https://www.facebook.com/Jeff.Grauer

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    The factory pump provides 3.4 to 4.3 PSI.

    We have our regulator set to 4 PSI and the car works well.

  52. #52
    Boat Anchor Repairman Captain Obvious's Avatar
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    Quote Originally Posted by Jeff G 78 View Post
    The two Facet pump numbers are 610-1077 and 610-1078. They are Facet pumps, but also have Napa branding on them.
    After much digging and cross referencing**:

    NAPA 610-1077 contains Facet pump number 40106
    NAPA 610-1078 contains Facet pump number 40104

    Slightly more info for those two pumps can be found here:

    http://www.facet-purolator.com/index...d=16&Itemid=31

    PART # MAX-MIN PSI GPH
    40104 4. - 1.5 25
    40106 7. - 4 32

    I still don't know what the specs mean, but here... This graph should clear it all up.



    This is what happens when Marketing asks Engineering for some documentation that they can put on the website that couldn't possibly cause anybody to actually be able to be held accountable for anything at anytime.

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    **Here's the NAPA page for the 610-1077 -
    https://www.napaonline.com/Catalog/C...077_0334661226
    on that page it lists the mfg #NAP12SV.

    Here's a pdf catalog from Facet/Purolator -
    http://www.facet-purolator.com/image...guide_2004.pdf
    At the end of that catalog it lists the solid state cube pump P/N FEP 12SV

    At this point, it's pretty clear that the NAPA 610-1077, Facet FEP 12SV, and Purolator PRO 12SV are all the same thing.

    Then on this page -
    http://www.facet-purolator.com/index...d=38&Itemid=62
    there's indication that the FEP12SV and PRO12SV are clamshell kits containing a pump number 40106 and other associated items.

    Similarly (without listing all the intermediate steps), the NAPA 610-1078 is a clamshell containing the 40104 pump.

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    Just found one more interesting piece of info. On this website (which looks like a Chinese second source to the 40106 pump)

    http://www.aliexpress.com/store/3011...re-shape-.html

    It lists a curious spec "Shut-off pressure : 4-6psi"

    The implication to me is that these pumps, being solid state and all, have actually got some pressure sensing technology in them and the pumping action is actually controlled to maintain the pressure between the two pressure points listed.

    In other words, the implication is that the 40106 pump will turn off when the outlet line pressure is above 7 psi, and will turn back on again if the outlet pressure is below 4 psi. And if you stay in the hysteresis band between those two limits, the pump will always run.

    So, if you've got a pressure regulator between the carbs and the return to the tank you just pick the Facet pump that has your regulators pressure at approx the middle of it's operating range.

    This is all inferred, of course.

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    I refreshed a clacker pump from a 240z and I vaguely recall some sort of pressure regulation inside with a spring.

    If you can monitor O2 when you hit high rpms, if it is lean then it is fuel delivery, if it is rich then most likely it is spark (un burned fuel).

    I had a 240z bog at high rpms and I thought is was fuel problem. I chased my tail checking everything and it turned out to be a spark issue.
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    Registered User Jeff G 78's Avatar
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    Wish me luck tomorrow. I will go through the list and see what I can do to fix the issue. I was able to find a Spectre regulator just like the one beermanpete showed earlier in this thread. I wasn't able to find a gauge yet, but I do have the little tiny 0-10 psi gauge that I can use until I find a bigger one. I will have lots of things to check and swap tomorrow and hopefully I find SOMETHING that gives me hope that the problem is fixed.

    Since I found a regulator, I will use the 4-7 psi pump and I have a new Bosch FI canister fuel filter from my '78 that I can use before the pump. It should provide good flow and have lots of filter media.

    Should I try to keep the return to start with and run the regulator in the return line? What about the mechanical pump - should I remove it right away, or keep it in series to start with?
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
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    1 to 10 psi should be fine if you have your fuel pressure regulator set - mine is below for reference if needed.

    Click image for larger version. 

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    Life's a journey; enjoy the ride!

    Mitchell
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    Quote Originally Posted by Jeff G 78 View Post
    Should I try to keep the return to start with and run the regulator in the return line? What about the mechanical pump - should I remove it right away, or keep it in series to start with?
    Hmmm... I'm no expert on this stuff and I would gladly defer to someone else who's been through this before, but I guess I would come out of the gate with this:

    • Mechanical pump still attached, but outlet routed back to inlet (because there's still residual fuel inside and you don't want it spraying on your cooling fan). And the reason I would take the mechanical pump out of the loop is because it may provide an unwanted restriction to the electrical pump, and in theory, the electrical pump should be able to provide all the fuel the engines needs, even at WOT high RPM, right?
    • Electrical pump mounted as close to the tank as possible (because the documentation for those cube pumps says that, while they are self priming and can do 12" lift, they are really pusher pumps).
    • Regulator located after the last carb pickoff point from the rail, and then outlet of the regulator returning back to the tank.


    Question... Are you running the original fuel rail? If so, what (if anything) are you planning to do with the original fuel rail "regulator" restriction orifice? If you're installing a real regulator elsewhere, I would remove that orifice. You don't want a pressure drop there anymore. You could drill it out or cut an inch off the end of the hard return line tip.

    And... "Good luck. We're all counting on you."

    PS - Crap! I was out late last night and didn't check the forum when I got in... Just looked at the posting time, and you're already on the track!
    Last edited by Captain Obvious; 10-01-2011 at 09:26 AM. Reason: Looked at the time...

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    Registered User Jeff G 78's Avatar
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    Quick update... No, the race isn't until NEXT weekend. This weekend is all about getting everything diagnosed and the pump installed.

    Facet pump is installed as WAS the Spectre regulator. Pump works fine, but the regulator appears to not work. With the regulator in place, no fuel flows past it. With it gone, the pump flows properly. The regulator has a In and Out marked which were checked.

    The carb inlets were clean and the float heights were fine per the FSM. I haven't tuned it yet due to yet another several issues. We installed a thermostat and one of the bolts felt soft upon tightening. Sure enough, it leaked and when removed, the housing was partially stripped. A Helicoil solved that problem and the leak is gone. Next, we readjusted the valves. Most were fine, but a few needed some minor adjusting after the track day and a fresh valve job. The next issue is that we started it up and it ran great, except we have no oil pressure or temp showing on the gauges. Before, the temp would climb to 120 and the oil pressure worked just a few days ago. They are both completely dead now. I can't see anything wrong, so now I'm off to check the archives for how to check the gauges. The cam lobes have fresh oil, so I know it's just the gauges. Everything is hooked up as it was a few days ago when they worked.

    We haven't made near the progress I had hoped today, but we still have time to get it done.
    Jeff
    Northville, Michigan
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    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
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    Jeff -
    Left you a PM........
    Life's a journey; enjoy the ride!

    Mitchell
    L28 - N42 Block w/Flat tops - N42 Rebello Head & Cam - Triple 40 PHH Mikuni's - Headers - Recaro Seats -
    R180 3.9 Diff - Close Ratio 5 Speed - Toyota Vented Brake Upgrade w/ Porterfield High Performance Pads & Shoes

    1972 Datsun 240z
    HLS30-75040


  60. #60
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    In for the night. It was a long day, but we made some progress, I think. Per my last note, the 4 - 7 psi pump is in place and working. According to my crappy little gauge, it is putting out about 3.5 psi with no load. I need to find a real gauge and a long hose to see what I'm getting on the track.

    I found the issue with the temp and oil pressure gauge. My teammate was cleaning up wiring and cut a power wire that fed them. Interestingly, the temp gauge does work. That means that for the past two years the temp has never gotten above 130F even when it was 80F ambient. With the thermostat in place, the temp gauge came up to just below the mid point just running it in the garage. I bought a 180F fail safe gauge BTW made by motorad. I think that's the same brand that MSA sold me when I bought one for my 280 a few years back.

    I still need to tune the carbs with the floats adjusted and the thermostat in place. I took the front fuel filter out to install the regulator and I then put it back in when I had to remove the regulator. It was the easiest way to make the hoses that I had work out. Prior to using the electric pump, the filter was always about 1/2 full, but now it's completely full of fuel. I guess that's a good sign that I have more flow. The mechanical pump is gone and we installed a block off plate. I still have the return line in use right now, but I will keep an eye on the pressure and block it if needed. I am still using the OE 260 fuel rail that is similar to a 280 rail with a return loop. If I quit using the return, I will need to come up with a safe way of blocking the hose. I guess I could install the regulator in it that won't flow anything.

    Tomorrow I will tune the carbs and check timing, compression, leakdown, vacuum, etc. At least I don't have any more leaks from the water neck. The helicoil did the trick. It's always good to have a M8x1.25 kit handy.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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    The temperature fix alone should make that engine run different and better.
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
    3.90 Subaru STI LSD

  62. #62
    Boat Anchor Repairman Captain Obvious's Avatar
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    The work sounds like it's going well. I like the part about the thermostat housing... It's always something!

    Quote Originally Posted by Jeff G 78 View Post
    the 4 - 7 psi pump is in place and working. According to my crappy little gauge, it is putting out about 3.5 psi with no load. I need to find a real gauge and a long hose to see what I'm getting on the track.
    That 3.5 psi is "engine running, sitting still, with return line in operation", right?

    About the thermostat, I wonder how much of a difference in required ratio the thermostat would make. By that, I mean... Is it conceivable that the change in temp from 130 up to 180 would change the optimum fuel/air ratio enough that maybe the carbs were working as designed all along, but it just wasn't enough fuel for an engine that was perpetually "semi-cold"?

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    Registered User Jeff G 78's Avatar
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    Quote Originally Posted by Captain Obvious View Post
    The work sounds like it's going well. I like the part about the thermostat housing... It's always something!



    That 3.5 psi is "engine running, sitting still, with return line in operation", right?

    About the thermostat, I wonder how much of a difference in required ratio the thermostat would make. By that, I mean... Is it conceivable that the change in temp from 130 up to 180 would change the optimum fuel/air ratio enough that maybe the carbs were working as designed all along, but it just wasn't enough fuel for an engine that was perpetually "semi-cold"?
    Correct on the pressure reading.

    I was thinking the same thing on the A/F without a thermostat. It really surprised me that the temp stayed so cold last year on the track. We ran a 14.5 hour race at 80F ambient and the gauge barely moved off 120F. The thermostat was in place with the valve itself removed. I would have sworn that it would have enough restriction to allow the engine to get up to temp. I guess I learned a tough lesson...

    I'll let everybody know how today goes.

    Thanks to all who have helped!!!
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
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    Not trying to be a di@khead, but I couldn't imagine not knowing the temperature of my engine(especially aluminum head motor) and intend to race this car. This is basics and you can't properly diagnose other issues without atleast covering the basics. Just about every tuning adjustment specified in any manual- specifies to warm the car to operating temperature.
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
    3.90 Subaru STI LSD

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    Marooned Fish cygnusx1's Avatar
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    Don't overlook your air intake system either. I have no idea what you are running, so I say this blindly. Also MUST confirm cam timing.
    Dave C, Putnam, NY
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    Registered User Jeff G 78's Avatar
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    Intake system is the stock '72 orange airbox. On the cam timing, keep in mind that this engine ran this way before and after a rebuild and with two different cams. I have rebuilt plenty of L6 engines, so I'm sure that it is correct. I matched both the bright links on the chain and verified everything physically before and after assembly.

    I agree that not having a temp gauge isn't good madkaw and I should have know better.

    For those who haven't followed my journey, this car was purchased as a complete basket case for $350 and was built from the ground up with virtually no money in 9 weeks. Every mechanical system on the car was either shot or screwed with by previous owners. The 9 week build included the car being gone for 2 weeks getting a cage installed. LeMons and ChumpCar World Series isn't like any other form of racing. It's all about racing real $500 cars, not who can spend the most money. Rather than stiff springs, race shocks and adjustable suspension, the stock springs were cut, the 25(?) year old dampers were kept, and suspension tuning was done with tall spring aid jounce bumpers and LCA pivot point relocations. Rather than rebuilding the engine, we tore it down to inspect and clean it and reassembled it with new gaskets only. The body was painted with Rustoleum applied with rollers and so on. Almost all of the parts that we did replace before the first race came from my vast stash of used parts. Gutting the thermostat is a common LeMons practice that *normally* works fine. The car has run well at times when it gets enough fuel, so low engine water temp was never considered as a cause for any of the running issues we've experienced.

    After the first few races and lots of track days, we have replaced a few things and recently rebuilt the engine, but for the most part, it's still nothing more that a $500 race car.

    Take a look at the build photos in this link http://www.facebook.com/media/set/?s...05972559430584 to see what we started with. Click on the first pic and scroll through them so you get the captions as well.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
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    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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    I honestly didn't realize this was a lemons car-very cool!
    My money is still on floats just need to be juiced up-throw out the you measuring tool
    Make sure your getting 14 volts to the battery.
    Get her to 180 degrees!
    I would suggest mechanical advance, but you've changed dizzys.
    Good luck
    Steve
    71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
    3.90 Subaru STI LSD

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    Not sure why the thermostat gets gutted? Might be off topic. The only reason I can think of, is to prevent it from failing in the closed position? I make lots of power in my stock motor with a stock thermostat and have no cooling issues; even on a road course. I am not good with SU's so I can't help there. I would suggest electrical issues in the coil charge circuit. Is the coil getting a strong 12volt charge, at speed? Plug wires, plugs... Good luck.

    Just thought of this after looking at the photos...is the throttle linkage opening the throttles all the way?
    Last edited by cygnusx1; 10-02-2011 at 12:49 PM.
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    Boat Anchor Repairman Captain Obvious's Avatar
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    I think the car is beeauuutiful and if I were closer to you, I'd offer to come to the race and turn a wrench or two. Would probably get in the way more than not, but I'd be there in a heartbeat to help out where I could.

    So are you going to be able to get any track time at all before the race to see if the fuel pump and/or thermostat made any improvement with your WOT at high RPM issues?

  70. #70
    Registered User Jeff G 78's Avatar
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    Hey Captain, you aren't THAT far away. The race is at Nelson Ledges in NE Ohio near the PA line which is about 5.5 hours from Philly.

    Yes, we have a Friday test day at the track to prove out our fixes.

    I raised the floats a bit, but didn't want to raise them way above the FSM specs. According to Bruce, the fuel should be 1/16" below the nozzle in the carbs when tuned. I raised the floats several mm, but still couldn't get them near 1/16". If needed, I'll raise them some more at the track.

    I have a question for those of you who have performance cams. My cam specs are .450 lift, 260/260 duration. What kind of vacuum do you get at idle? I'm getting about 13" hg which would be low for a stock cam, but I can't recall what it should be with that cam.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
    https://www.facebook.com/Jeff.Grauer

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    Hi Jeff,

    I took a look at a map and it's not "close", but it is closer than I thought. I don't think I'm going to make this one on short notice though. I should have started thinking about it two weeks ago in order to have arrangements in place.

    As for your cam, I have no idea. Again, I'm very surprised that you haven't gotten lots of responses from people who have done cam swaps!

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    Quote Originally Posted by Jeff G 78 View Post

    [edit]

    For those who haven't followed my journey, this car was purchased as a complete basket case for $350 and was built from the ground up with virtually no money in 9 weeks. Every mechanical system on the car was either shot or screwed with by previous owners. The 9 week build included the car being gone for 2 weeks getting a cage installed. LeMons and ChumpCar World Series isn't like any other form of racing. It's all about racing real $500 cars, not who can spend the most money.

    [edit]
    You know, I gotta admit when I began following this thread and responding, I was beginning to wonder if you were sane or that perhaps it was some sort of social networking experiment.

    All is clear now.

    Run those "works" teams into the ground!



    Chris

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    I want to thank everybody for your help and support. The Z is on its way to the race and I am just awaiting another teammate with the camper to arrive at my house. We should roll into Nelson Ledges around 11pm tonight and we'll know tomorrow if it runs right.

    I won't likely have any internet signal, but if I do, I'll let everyone know how it goes tomorrow. The race starts at 10am Saturday and finishes at 12:30pm on Sunday. Other than an hour safety break to rotate corner workers, we go straight through for a total race time of 25:25:25. Fingers crossed...
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
    https://www.facebook.com/Jeff.Grauer

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    Registered User beermanpete's Avatar
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    Good luck and have fun.

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    Excellent. I hope you have those issues licked and have all the horses you're supposed to have. No rolling chicane for you!!

    Good luck!

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    I'm WAY too tired to go into the details, but the car ran terrible at times and great at times. In 25 hours, 25 minutes and 25 seconds (25:25:25), we completed 698 laps for a total of just under 1400 miles! We finished 30th out of 75 entries and had a great time. The handling was amazing and the motor ran great at night when it was cold. We had terrible vapor lock and other heat related fuel issues in the heat of the day.

    Thanks to all who helped and I promise to give a full race report with the symptoms and fixes once I get a shower and some sleep. I haven't done either since Thursday.

    BTW, we won the Mr. Clean award for the cleanest driving. The Datsun only has one scuff in the fender and a chunk out of the front bumper. Both were caused by other drivers sliding into us in the middle of the night.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
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    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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    Congrats! Sounds like a great time was had.
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    Sounds fantastic. Well, other than the vapor lock stuff of course.

    Looking forward to the full report!!

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    Hey - What's your Chump Car team name?

    I run with SkoolBoyZ Razing down here in Florida in an old ratty 280z.

    Just noticed your post...

    One thing that I've seen in 3 separate Z's

    I bought a pristine 260z from California from the original owner many years ago. He complained about all the things you have experienced and said Nissan couldn't figure it out for over 10 years.

    When I got the car I eventually found the problem...

    When we opened the fuel tank (and I've seen the same problem 3 times since) there was a slight "kink" in the pickup tube inside the tank. If any sort of debris was sucked up, it could not make it past the kink... let the car sit and it the debris would sometimes fall back to the bottom of the tank... so it presents itself like an intermittent problem... or sometimes just a fuel starvation problem with restricted flow.

    I used a 2 gallon fuel cell and hooked up my pump to it, bypassing the stock tank and tested it that way...

    Also, when I blew compressed air from the line on the suction side (fuel rail) back into the tank, I suspected a restriction because once I blew out the debris it would go away temporarily...

    Draining the tank and inspecting with a scope always looked like the tank was perfect inside - wasn't until we cut it open that we found it...

    Also, I suspect your float settings as a secondary problem...

    Good luck and keep us posted

    Would be good to know what your AFRs look like

    Another item to suspect is your distributor/ignition box/ignitor -

    Ken

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    Registered User Jeff G 78's Avatar
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    OK, be prepared for a long post...

    We went out on the track Friday morning for practice and the car immediately exhibited the same issues as before. We pinched off the return line with no improvement and kept trying different things to no avail. At one point, we went to restart the car and the battery was dead. We checked voltage and it appeared the alternator was not working. We had a new one with us, so we installed it with no improvement. We then swapped the voltage regulator with no luck before we started tracing back every wire in the car. The problem turned out to be a missing wire that was removed during wiring cleanup. A teammate had inadvertently removed the wire that powers the alternator! With the wire back in place, we were once again charging and we figured that our high RPM issue might have been caused by low voltage to the coil. It was now 4pm and we still had to go through tech, so daytime practice was over and we had very little track time. We got through tech and prepared the car for night practice which started at 7:30pm. The car ran way better and we thought we had been chasing fuel issues when it was really low voltage this time. We swapped tires and did the final checks Friday night before we hit the sack.

    Saturday morning came and we took the green flag at 10am. The weather was beautiful, and the air was still cool. There is a 2 hour driver stint limit and with our new tank, we should be able to run that long, but after 1.5 hours, the driver radioed in saying he needed fuel. The car took only 10 gallons to fill and we were back on the track. He said that the car ran well and made power to 6500 RPM, but it stumbled off turn 13, the tight right-hander leading to the front straight. The second driver again went 1.5 hours and used 10 gallons of fuel before the car began to backfire on decel and sputter out of the turns. By now, it was a little after 1pm and the temperature was up into the high 70's with bright sun. The car began running worse and worse on the straights going back to its old habits of not revving past 5000 RPM. This time, when the driver came into the pits for fuel and stopped at the beginning of pit road to get his timer, the car died(they put a magnetic timer on the roof of every car entering the pits to make sure you spend a full 5 minutes in the pits for fuel stops). We pushed the car to our pit stall and fueled it up. When he tried to restart, it had all the signs of vapor lock. The car tried and tried to start, but wouldn't keep running. We lost almost 15 minutes before we finally got it going. We cycled through the drivers and it kept running worse and worse through the day. At every fuel stop, it would refuse to restart hot and we kept losing time. Our fuel pump was struggling to prime and fuel pressure was sometimes good and other times not during engine restarts. We tried every combination of return open and closed. We then decided to go back to the paddock and install the mechanical pump in series with the electric pump. We lost a lot of time and when we finished, it made the problem worse, not better. At was now 5pm and the race was checkered for a 1 hour safety break to rotate corner workers. After a 15 minute drivers meeting, we got busy making changes. We removed the electric fuel pump and made a bracket to drop it down a foot lower to be right at the height of the bottom of the fuel tank. We were sure that the pump couldn't lift the fuel to prime once we got low on fuel and sucked some air. We also removed the mechanical pump again and we were ready for the 6pm restart.

    I finally got my turn at the wheel after the restart and the car ran great other than the stumble down the front straight and back straight after right hand turns. All was fine for 20 laps of so until a full course caution and the safety truck came out. The truck was going very slowly and we came to a full stop as we waited for a tow truck to extract a car from the mud. As soon as we stopped, the car died on me and wouldn't restart. I was dead in the center of the track with classic vapor lock symptoms. I tried for several minutes to refire it on the track, but it wouldn't catch and I had to be towed back in. After we iced the carbs and it cooled a bit, it fired back up and I was back on the track. It ran great other than the two stumble spots. As my stint finished, it was just getting dark out.

    It is now 7:40pm and it's dark out. We are in 50th position out of 75 teams. The temps began to drop right away and the car ran better and better. We never missed a beat over night and by sunrise we had climbed to 39th place. The stumbles went away completely by the time I got my next stint at 3am and the car was running perfectly. It made power to 6500 and was able to keep up with most of the other cars. One thing that showed up in the night was that when we came into the pits and popped the hood, the exhaust manifold was always glowing BRIGHT red. I assume this was happening all race and we could only see it at night, but I can't say for sure. Now that we lowered the pump, we never had any priming issues and we could use more of the tanks capacity.

    Sunrise over Northeast Ohio and the race was stopped for a quick drivers meeting. Overnight was some of the worst driving I have ever witnessed on a racetrack. There were cars going off everywhere and in the first 17 hours of the race, we had 6 rollovers!!! All teams got a stern warning to stop driving like asshats and we were back to racing. We kept gaining spots and we were in 37th place at 8:45am. The next to last driver got in the car and ran his 1:45 stint. He came in at 9:25 and said that it was starting to stumble more and not rev all the way. He also said that the tires were really losing grip and that I'd have to go longer on gas than anyone else was able to do and just bring it home with what I had to work with. I got in the car to finish the final 2 hours of the race at 10:30am. The car was running even better than it did overnight and unlike overnight, I had a lot of clear track to work with. It was the best 30 minutes I have ever had on a race track. I had several close calls though. After only a few laps on the track, I entered Oak Tree, a banked left hander, in the outside lane and I there was a very fast V8 inside of me. I heard his tires howling and I knew he wasn't going to hold his line. He slid across the track and I was prepared to get hit. He nailed me in the rear bumper and I quickly corrected and saved it. He got the black flag the next time by the start finish line. After another few laps, three other cars spun right in front of me and I was always able to avoid them as they blocked my path. Unfortunately, I lost communication with my crew only a few minutes into my stint, so I had no idea how long I had been in the car or how much time was left in the race.

    Not knowing how long I had been in the car, it started backfiring on decal and really stumbling coming out of corners. This is exactly what it does when getting low on fuel. With no pit communication, I ducked into the pits to get fuel. This was the wrong thing to do! As soon as I cam to a stop at our stall, the car died. I asked how long I had been out and the answer was only 45 minutes! Oops! There is no way I was low on fuel, so the problem was simply that the car running poorly due to the hot weather and ongoing fuel issues. The car refused to restart for several minutes. I got back on the track with my communication working again and I just drove what I had and worked around the poor running. With my poor decision to stop, I lost 2 positions. I ran the car as hard as I could and took the checkers after 25:25:25.

    We finished in 30th place and logged 698 laps and close to 1400 miles. In the awards ceremony, they again scolded the field for terrible driving and said that nearly every car in the race was damaged. The ChumpCar staff had talked it over after the race and asked the corner workers if there were any cars that didn't have any damage and were never called out for going off track or running into anybody else. They concluded that only one car ran a truly clean race and they announced the #46 Broke Racing Effluence Datsun as the "Mr. Clean" award winner. It was really cool getting another award. Last year, we won an award for the best looking car.

    After the race, we spoke with many teams who told us how pleased they were with our driving. We took the oldest car in the field by a decade and completed the longest endurance race ever. We were never fast on the straights, but I'd say we have the handling dialed in near perfect. We started the race on used 195/60R14 Falken tires that ran our first 24 hour race two years ago. They ran 185 laps in that race and 698 laps in this race and they are still not to the wear bars and they have worn perfectly evenly across the tread. The Porterfield R4-E brake pads have now run 14+ hours at GingerMan, two track days, and 25+ hours at Nelson Ledges. We never even replaced the brake rotors that were on the car when we bought it two years ago.

    We were ecstatic with our race overall and we will figure out and fix the issues before next season.

    Thanks to all who helped us!
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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    Registered User Jeff G 78's Avatar
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    I forgot to discuss a few more details about the running issues.

    One thing we noticed is that during normal operation, our temp gauge reads about 180F, but at track speeds, it reads only about 130F. This is with a brand new 180F thermostat. The engine is clearly getting plenty warm if the exhaust manifold is glowing red, but why is the water temp so low?

    To try to help the vapor lock issues, I made a heat shield that protects the fuel bowls from the exhaust heat, but it didn't help at all.

    When we had our high RPM issues, I replaced the bowl to nozzle hoses with stiffer clear Tygon hose with no improvement.

    At about 5am, I had a nice discussion with a fellow racer who knows old Japanese carb cars very well. He said that our stumble exiting corners is due to "spill over", a condition where the floats are set too high and the fuel is forced up the nozzles in long corners. The car goes rich in the corner and the plugs get wet. It takes several seconds for the plugs to dry and fire properly again causing the acceleration stumble after a hard corner. He went on to say that to lower the floats, I need to drill the jets bigger to allow fuel to flow into the bowls faster to avoid the high RPM starvation. Raising the floats like I did fixes one problem, but causes another. It was a good trade-off, but drilling the jets out and lowering the floats a bit should let it rev as well as fix the stumble.

    We will make a more permanent bracket for the fuel pump (the current one is really chumpy as it was made in 10 minutes from 22 gauge sheet metal), but we still haven't figured out how to fix the fuel temp issues. The return system doesn't help the fuel that's sitting in the bowls.

    Why is the exhaust manifold so hot? Is that normal? Hot normally means lean, but we already have SM needles and have fattened it up by raising the floats.

    Even when running perfectly, we really need more power, so we might have to look at a L28 or even a turbo L28. We just have to do it on a shoestring budget to stay legal.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
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    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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    Glowing exhaust means it's rich. If you're burning fuel inside your manifold, it will literally get red hot! As far as the vapor lock issues, try to insulate all fuel lines, and don't mount the fuel lines to anything attached to the engine. The original fuel rail will conduct heat from the engine to your fuel lines if you're still using it.
    2/74 260Z

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    And congratualtions on the finish and award. Sounds like hell, errr fun!
    2/74 260Z

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    Rich? Hmmm, I always thought that hot exhaust meant lean. Makes sense, I guess. And yes, we are still using the stock rail. I guess it's time to ditch that too. It's still bolted to the head in the stock four locations.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
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    Registered User LeonV's Avatar
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    Quote Originally Posted by Jeff G 78 View Post
    Rich? Hmmm, I always thought that hot exhaust meant lean. Makes sense, I guess.
    Yes, the mix up may come from the fact that combustion chamber temps reach a maximum just above stoichiometric and exhaust temps are a max below stoich.

    Quote Originally Posted by Jeff G 78 View Post
    And yes, we are still using the stock rail. I guess it's time to ditch that too. It's still bolted to the head in the stock four locations.
    There you go, that's 4 paths of conductive heat transfer right from your engine to the fuel lines. No amount of heat shielding will stop that. Hopefully, eliminating the stock rail and routing your lines in a way to limit heat transfer into them will alleviate if not fully cure your vapor locking problems.

    Out of curiousity, did you try running the car with the hood propped open to vent heat?
    2/74 260Z

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    Registered User Jeff G 78's Avatar
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    No, we didn't try anything with the hood this time. We did try it in the past, but that was before any of the recent changes. We don't have a hood latch and we run hood pins, so we'd have to remove it and we have lights mounted to the front of the hood, so we'd have to unhook the wiring to those as well. We did consider taking a cutoff wheel to the hood and cutting a big hole over the carbs. I'm pretty sure I still have a vented '78 hood, so we might paint that one up and use it instead for future races.
    Jeff
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    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
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    Marooned Fish cygnusx1's Avatar
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    +1 on the L28ET swap. How big is your shoestring budget for the swap? I can detail the swap for you if you want.
    Dave C, Putnam, NY
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    Registered User Jeff G 78's Avatar
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    Dave, I need to research the rules and see how much a turbo is worth to the budget. Then I need to spend the winter searching CL and ebay ads for cheap Z cars. ChumpCar uses a system called AIV or Average Internet Value. We have to produce ten ads for cars like ours and the average ASKING price is your AIV. The cars must run to qualify and they must be the same make, model and option list. For old cars like the Z, they allow us to use all S30's even though they might have different engine sizes than the car we run. For this race, I came up with an AIV of $415. That means I could have $85 worth of mods for a $500 max value. Keep in mind that COST never factor into AIV. It's all about VALUE. In other words, if I buy a Rebello stroker motor from a friend for $85, it's not going to fly. They have value assigned to many common upgrades. Have aftermarket bars? They are worth $50 each. Springs, camber plates, and other mods have similar minimum VALUES assigned. I say minimum because the value can go up if they are more than cheap aftermarket parts. Chinese ebay coilovers are worth far less than real race coilovers, for example. I have never seen turbo values listed, but a junkyard turbo motor can be had for what, $150? That means I'd have to get my AIV down to roughly $350.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
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    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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    Marooned Fish cygnusx1's Avatar
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    Running, turbo motors are probably more than $150. I would say that a greasy, well used, running, turbo motor with its ECCS injection system, would average around 500-1000. It will make the car much, much, quicker, so I suspect that you will take a pretty large penalty from the race organizers. Then brakes and tires become an issue as well. Considering your great placement at the end of this last race, you may already be sitting on the correct formula. Maybe you just need some spit and polish.
    Dave C, Putnam, NY
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    Awesome! It sounds like you guys had a great time overall.

    Are you using the Falken Azenis RT-615? We have been thinking of trying them.

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    Yes, that's what we run. We still use the old RT-615, not the new RT-615K.
    Jeff
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    Hi Jeff,

    Thanks for the fantastic race report. Congratulations on your finish position, and your Mr. Clean award! Sounds like a load of fun, although frustrating at times. That's the problem with not being able to test under the actual use conditions.

    I know it's way out of your budget, but could you run a wideband? After the stuff you describe, it's unclear if you are running too rich or too lean. Your 5:00AM discussion buddy thinks it rich, and backfiring on decel and your glowing manifold would corroborate... You could use it for test and practice laps, but then take it off for the actual race laps? Would that count against your $$ ?

    So what's the bottom line on performance...

    When it's cold, it runs great. No stumbles at all and no restart issues. Makes power all the way to 6500 RPM.
    When it's hot, it stumbles out of turns (right turns only?) and is hard to restart hot. Breaks up above 5000 RPM.

    Are you running any of the original emissions controls? I assume you've already nuked EGR and air pump, but are you still running AB valve or throttle opener controls? I'm thinking that the elimination (or non-functioning) of those two might load up the plugs and exhaust manifold with unburned fuel on deceleration.

    And I agree that a vented hood would be a good idea in the future. Probably won't do a whole lot once you're up to speed, but could help a whole lot at low speeds and when you are stopped completely like at pit stops and driver changes. Especially if you've got to keep the engine running for five minutes while sitting dead still.

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    You are on the right track. We will probably install a wideband O2 sensor to see what's going on. It doesn't count against us as it's considered information only and doesn't affect the performance. One suggestion I got from a fellow CC racer is that we are cooking the fuel due to the use of the stock fuel rail which is bolted to the head in the original four locations. All of that head heat is transmitted right to the metal rail and is then captured by the OE heat protecting wrap. I'm sure the rail was probably too hot to touch, so it makes sense.

    We don't run any of the OE emissions equipment. The EGR and air pump are gone as are the rest of the stuff. The "spillover" theory that a racer told me makes the most sense. It's when the car goes rich mid-turn due to high float heights and then sputters off the corners until the plugs dry off. I will talk to Steve and Bruce at ZT and see what they say.

    Our biggest problem is that even at night when the car ran damn near perfect and we turned our fasted race lap, we were STILL 12 seconds off the leader's best lap and the slowest "fastest lap" of any car. Granted, there was only a 10% spread through the field, but we are still too slow. I'm thinking that we could improve the overall running and eliminate the lost laps due to vapor lock, but it won't be enough to even be a mid-pack car in lap times. We need more HP. We can either try to eek out what we can with the L26, swap in a L28ET, or go radical and swap a V8 or other motor in the car. I would really rather not go the V8 route, but I am not against a turbo swap. After a quick CL search, I found a <100k turbo motor for $500. I'd rather find a whole ZX Turbo, but those aren't exactly common in the rust belt.

    Thoughts???
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
    https://www.facebook.com/Jeff.Grauer

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    After a few emails back and forth to my teammates, it sounds like in 2012, we will be sticking with the L26 and tuning it better after getting all of the fuel issues worked out. If it's still too slow, then we will upgrade next off-season.

    Any recommendations for a Wideband O2?
    Last edited by Jeff G 78; 10-12-2011 at 10:40 AM.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
    https://www.facebook.com/Jeff.Grauer

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    I've never personally messed with a wideband, so I'm not qualified to provide suggestions there.

    I did come up with a question about the problem in the turns though... You said that it goes rich mid-turn. Are you already on the gas at that point when it starts acting up?

    I, for one, am glad that you are sticking with the L26. Frontrunner or not. You're period accurate, and I think that adds class to your team. Of course, that doesn't add any speed, but I think it adds credibility.

  96. #96
    Registered User Jeff G 78's Avatar
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    Yes, it acts up under hard throttle. The explanation I got is that the plugs get wet while leaned over hard and then it takes a few seconds for them to fire properly again.

    I would love to see us keep the L26 AND be competitive, but I'm not sure we can do that without spending big bucks on the engine which we won't do.

    I went through the lap report today and if I remove all the lost time stuck in the pits due to vapor lock alone, we'd gain over 100 laps. That would have moved us up from 30th place to around 13th place. Fix the other fuel delivery issues to make the car run better and we could have been a top 10 car without actually being much faster than we are now. We still would have been down close to 100 laps to the winner, but it would be a respectable finish.
    Jeff
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    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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    Boat Anchor Repairman Captain Obvious's Avatar
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    Quote Originally Posted by Jeff G 78 View Post
    if I remove all the lost time stuck in the pits due to vapor lock alone, we'd gain over 100 laps. That would have moved us up from 30th place to around 13th place. Fix the other fuel delivery issues to make the car run better and we could have been a top 10 car without actually being much faster than we are now.
    Absolutely. That's beyond "respectable" and into "enviable".

    I looked at the float geometry last night to refresh my memory, and I'm not seeing an obvious explanation for mixture changes under lateral G's. At least nothing that wasn't symmetric side to side. Because of the direction of the float hinge pin and the position of the hinge on the float itself, I could maybe see something under hard acceleration or deceleration, but side to side isn't obvious. Not saying there isn't a relationship, just saying that it doesn't jump out at someone not trained in the art like myself.

    I'd love to hear what the experts like Steve and Bruce at ZT say when you talk it over with them.

    I thought of something I should have suggested a long time ago... When you are having the stuttering problem, have you reached for a handful of enrichment cable? That could tell you if you are rich or lean while the problem is occurring. If the problem clears up when you pull the choke and lower the nozzles, it's pretty clear that you are starving for fuel. Vice-versa for making the problem worse if you're already drowning.

    Out of curiosity, what was your average gas mileage? You said your drivers were getting roughly 1.5 hours out of ten gallons of fuel. About how many miles is that?

  98. #98
    Registered User Jeff G 78's Avatar
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    I should have been clearer when I said the problem was after right hand corners. Nelson Ledges is a VERY fast track and it flows very well turn-to-turn. The one RH turn is very tight and leads onto the front straight and the other is a 180 banked turn leading to the back straight. I'm not sure that the direction of the turns was a factor as much as the loading followed by a hard acceleration run.

    I did not try to open the enrichment (choke) THIS race, so I can't say if it would have helped. I have tried it in the past when the car wouldn't rev past 5k RPM and it did not help.

    I haven't gotten the fuel logs yet from my teammate, but when I do, I'll calculate the GPH (gallons per hour) and MPG. GPH is the standard race terminology since that's what matters to us. I'd say we are about 7 GPH which is in the ballpark for our car.
    Jeff
    Northville, Michigan
    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
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    Just throwing something out there. You said you are using the stock fuel rail, it should be the same as my 73. Can you modify it? For example, the front 2 mounts have steel pads, can they be removed and replaced with heat resistant material, ie carb & fuel pump? Use the same material between the head and bracket on the carb side. The bolt itself would have some transfer. Heat resistant bolts? Do all 4 mounting points need to be attached? Using the original silver heat resistant wrap? Just a few ideas.

    Bonzi Lon
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  100. #100
    Registered User Jeff G 78's Avatar
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    Hey Bonzi, yes, the plan is to do exactly what you said. The plan is to remove the steel pads from the front rail mounts and replace them with some sort of insulators like the carb/fuel pump spacers. If I drill out the holes in the rail mounts and run the insulators on both sides of the rail brackets, I think the heat transfer through the bolts should be greatly reduced. There is no need to run all four mounts either. 2 or 3 should be plenty. I am still running the OE silver asbestos(?) wrap. I will replace it with a more modern heat wrap to improve the insulating properties.

    I am thinking about engineering a simple loop cooler and pump system that would run a water pipe along side the fuel pipes in the rail and under the heat wrap. I would make a loop in the airstream, install a small reservoir and use a tiny electric pump on a toggle switch. It could be switched on only at high ambient temps or during pit stops to keep the rail cool.

    Anybody ever tried this?
    Jeff
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    IZCC #1285
    '78 280 10:1 CR, Arizona Z Car header, urethane bushings, Tokico springs, Illumina struts, Panasports w/Hankook R-S2 225/50R16 tires, Maxima 105 amp alternator
    http://www.classiczcars.com/photopos...00&ppuser=7975
    '74 260Z BRE look-alike crap can for Optima Batteries ChumpCar World Series Racing racing
    https://www.facebook.com/Jeff.Grauer

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