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Thread: Gas Depth in Float bowl, when excluding float volume

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    Default Gas Depth in Float bowl, when excluding float volume

    I am having one heck of a time getting my 240 tuned up. I have a 72 with 3 screw SU's, and E88 intake manifold, pertronix ignition set to 17 btdc, and new NGK plugs gapped to .032". On top of that I have replaced my fuel filter, added all new rubber lines, and thoroughly blown out the hard lines. Also, I have 20 wt oil in the dashpots.

    Before I figured out Bruce at Ztherapy was the way to go I picked up some GP Sorensen carb rebuild kits and replaced all of the seals in my carbs, cleaned the screens and reset the float bowls per the rebuild kit instructions. Which at the time said 14.28 mm, this allowed my car to run with the choke open, but I could never get the car set rich enough. It always wants to die with the lift pins up on either carb. Even if I run the mixture adjustment nuts underneath are turned all the way out.

    When looking at the notes on http://www.teglerizer.com/sucarbs/techtip6.htm. I noticed the fuel level is supposed to be at 22-24 mm below the cap of the float. After using a piece of fish tank line I was able to find my level was at 30 from the top at the rear and around 35 on the front carb. This was done by pouring gas into the fuel line, not pressurized by the mechanical fuel pump.

    I was able to screw around with the floats and ended up with 9.5 mm front and 11.5 on the rear carb to get the gas level closer to spec. Though Way out of float height spec per the manual. With these settings and the front pin lifted the car will rev up and then idle back down. Though in all honesty the mixture nut can be all the way up or all the way down and it wont make any differance.

    The front carb appears to be doing nothing at all. I am getting spark to the front 3 cylinders, but pulling the wires wont change my idle. I dont appear to have an intake leak (I fixed it a night or so ago) as it wont change idle if I spray starting fluid or carb cleaner near the manifold. If I spray starting fluid directly into the carb it will start to stutter almost as if I am flooding the engine. Also, when lifting the rear pin the engine dies almost immediatly. I have tried 2.5 turns out as a start, all the way down and get nothing all across the range.

    Both carbs have been synced at idle and at 1500 RPM with no problem. I guess to get to the point. Does anyone know what the level of gas should be in the bowls if you have removed the floats? Should I go back and try to reuse my factory float valves? I am not real confident in running the car with my little fish tank line and gas hanging out above a hot exhaust manifold. Oh, and the fact that it only runs on the rear carb doesn't help with that anyways

    On lighter note, my son was born two weeks ago today and my car has taken a back seat to him!
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    Sorry, no help with the problem. Bruce will chime in I'm sure. BUT what a cutie-pie!! Your life has now changed forever. Speaking as a Dad of 3: 44, 41, 30, and the Grampa of 3: 12, 5, 3, you will never stop being a dad. Welcome to the world baby boy.
    Cheers, Mike
    and congratulations.

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    Thanks, it has definately changed a ton. I was hoping to get everything knocked out on the car before he got here, but he came 2 weeks early and pretty much stopped me in my tracks. He was at 38 weeks so baby still came out perfect...well other than the fact he poops and pees everywhere all the time!

    I am sure you are enjoying your grandkids, my parents can't beleive how much they love mine already.

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    Congrats on the birth. Parenthood is awesome. But so are 240's and SU carbs....

    Have you tried removing the carbs and cleaning them? If the fuel bowls have fuel, but the mixture screw has little or no effect, I suspect a clogged jet. Seafoam or other additives wont help here. You will need to open or replace any clogged orifices.
    Gary
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    I have cleaned the top half of the carb as much as possible. When I had the replacement hoses from the rebuild kit on the carbs I was able to squeeze them a little to get fuel to come out of the nozzle. This was both while the engine was running and viewed from above with the carb apart.

    The bad part is they both sprang a leak so I am back to temporarily using 1/4" line on the bowls to nozzles that was on the car when i bought it.

    When I spray starter fluid in the front carb it bogs the engine....could I be so rich that my front cylinders arent actually igniting the mixture throroughly and it just seems like I am not running on the front carb?

    I know that when I had the intake leak spraying the front half bogged the engine, while the rear revved up slightly.

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    Spraying starter fluid in a running engine can be dangerous. Don't do that anymore, please.

    When you say that you cleaned the top half of the carb as much as possible, are you referring to the outside or the inside? I'm suggesting that the carbs be removed, disassembled and clean the internal jets & passages. While the carbs are off the car, they will be easier to inspect.

    This may not solve your problem, but it will eliminate one possibility.
    Gary
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    I pulled the dome and piston section apart cleaned all the passageways as much as possible with carb cleaner and shot carb cleaner down into the nozzle until it poured out the line. While I had it apart the float valves were replaced as well.

    The only thing that hasnt been dissassembled is the nozzle assembly. Which I have heard is a PITA to put back together afterwards. Also, it already moved quite smoothly with the replacement lines on it.

    I was only giving it a small spray, not a full on blast, but I see how that can be dangerous either way and will cut it out.

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    I made a new bowl sight out of a drilled out bolt, right angle brake bleeder fittings, and some fish tank line that allows me to get a much better reading with the engine running. I have the front carb set to 23 mm on the dot and the rear carb is closer to 22, but I am still getting the same sort of problems. The front carb appears to be working fine at a 1k idle, however if I drop it down to 750, it doesnt do much if anything.

    What doesn't make any sense is that when I lift the front pins the engine idles up and then drops down to a near normal level in a couple of seconds. Is there anything that would cause it to not be idling on the front carbs and yet have the mixture set right per the normal instructions?

    The rear carb is idling much better than before, but I still can't get the RPM blip to happen when I lift the pin.
    Last edited by hogie; 05-11-2010 at 10:06 AM.

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    Vacuum leak. Is everything properly connected?

    Are the nozzles moving correctly? Do you have a restricted nozzle or fuel tube?

    Are the needles seated properly in the slide?

    Is the based seated against the spacer well? Have you tried spraying the base with carb cleaner (while the engine is running) to see if the idle increases? I'd spray the butterfly as well.
    Gary
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    No more vacuum leaks that I can find. I blocked off the vacuum to brake booster to make sure I didnt have a problem there as well. I then double checked that my intake manifold and throttle shaft bushings didnt have a leak by spraying them with the carb cleaner. There wasnt any perceptible decrease in idle.

    The rear nozzle is a bit stiff, but was pushed up as if the choke was off.

    I have used a straight edge to set the shoulders of the needles flush with the bottom of the piston. I have also tried loosening the needle and using the bottom of the nozzle to set the position. It seems to run the same both ways.

    I am not sure by what you mean with the "base seated against the spacer well". I assume you mean is the jet centered and the piston makes a good thunk when dropped on either carb.

    If you spray carb cleaner into the mouths it will decrease the idle on both carbs. Starter fluid (which you said not to do) will increase the idle.

    Thanks

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    Quote Originally Posted by hogie View Post
    I am not sure by what you mean with the "base seated against the spacer well". I assume you mean is the jet centered and the piston makes a good thunk when dropped on either carb.
    Where the base (side) of the carb connects to the manifold. If you have a bad gasket or spacer it will cause a vacuum leak.

    It seems as though you have covered all of the bases of carburation, so you may need to start looking at other symptoms. I went back to your first post. You say that you can sync the carbs at 1500 rpm, but not at idle. You also mentioned that "the front carb appears to be doing nothing at all." Can you elaborate on this? Do you mean that the engine only appears to be running on the three rear cylinders, or that you can not change the idle on the front carb?

    Have you checked your linkage to ensure that the idle screw is in fact changing the butterfly opening?

    Is the engine running smoothly?
    Gary
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    I havent tried spraying the bottom of the carb manifold connection, and I have new gaskets, so I may as well. I have no problems syncing them at any rpm currently.

    At around 750 rpms, if I pull the front plugs the rpm wont drop. Also, if I pinch off the fuel line the rpms don't change dramatically. The rear carb does most of the idling. At 1000 rpm or so, this is not the case and the engine rpm will change if pulling the plugs or cutting off fuel.

    Oddly enough it will sometimes idle just fine on the front carbs, but more often then not it doesnt. For instance if I use Beandips method of carb tuning and lift the rear carb all the way it will usually die or come really close.

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    I think its time for a compression check.
    Gary
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    Already done with a crappy, non accurate Autozone rental. It was consistent across the board at 100. Which I know is low, but the meter was reading way low compared to a known air source i.e. my compressor. From what I remember it was reading around 70 when I was blasting 120 into it (with no leaking)

    So yeah, I dont know the exact compression, but that it at least is close from cylinder to cylinder.

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    The reason I asked about the compression check is it sounds like you've hit the usual suspects on the carbs.

    A fuel pressure check might be helpful. You may have low pressure at low rpms and the rear carb is the only carb to receive fuel. As rpms increase the fuel pump can deliver enough pressure.

    You mentioned that you can remove the first 3 plug wires with no effect below 1500 rpm. Have you checked for spark? I assume you have spark if you were able to run a timing light off #1.

    Fuel, air, compression & spark. A problem with any one and you have a non-runner. The question is which don't you have below 1500 rpm.

    Check that fuel pressure.
    Gary
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    I did not read thoroughly every post here, as I don't have time to get too tied up while here at work. But in a quick scan I did not see any reference to checking for vacuum leaks at the throttle shafts. If the shaft bushings are bad, trying to get it running right at idle can be nigh impossible.
    Arne - Former owner, HLS30-37705, 7/71, 905 Red
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    The throttle shafts seem to be fine and i am getting spark on all cylinders. Both as tested by timing light and getting the plug wires to arc.

    I've got baby duty tonight so i wont get a chance to do anything else tonight. Tommorow i will try to pull the carbs and flip sides on them and see if the symptoms do too. After that another good soaking and new rear gaskets. I also picked up some nice honda fuel line to avoid future fires.

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    Can we get some close up photos of the carbs? I'd like to see the underside, the linkage and any other views you could provide.
    Gary
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    Quote Originally Posted by hogie View Post
    The throttle shafts seem to be fine...
    I'd test them for leaks. With the engine idling, spray a little WD40 (or your favorite substitute) at the shaft pivot points, on both sides of both carbs. If the idle changes (either up or down) during this process, the shafts are leaking unmetered air and you will never get them adjusted correctly.
    Arne - Former owner, HLS30-37705, 7/71, 905 Red
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    Congratulations to the most extreme event of your life!! The highest high you will ever have - my son is 24 and I am still in awe of the total experience! What a God given high.........amazing and woderful!! Be ready for a great adventure for the rest of your life - it only gets better!

    A few questions:

    How are you measuring your air flow? What tool are you using? I use a:
    http://www.cbperformance.com/catalog.asp?ProductID=572

    Is there any blockage of your nozzles? (Have you removed them and looked)?

    Have you put some grease on your nozzle bodies?

    Is your choke moving correctly ?

    Are your pistons moving freely or are they sticking at all?

    What floats are you using? - in part of your thread you stated that you could put the originals back in??

    Are you getting flow out of the fuel lines going into both carbs?

    If you had only one carb working you would be running off of 3 cylinders and running extreemly rough - are you running smooth when running?

    I am running a L28 with duel Hatachi's and an E88 intake with points:

    I just set my float bowls last month and the front at 9/16" and the rear at 1/2" (both on the heavy side of the line) - after a little adjusting of my idle adjusting nut I am pretty good now - a little phat but not too crazy. I think most of the Z's run a little phat anyway

    I used a cardboard cutout measured and set the lid upside down and insert the cardboard cutout to sizing (I also replaced the seat and needle valves). You may need to make sure your seat and needle valves are working correctly and not blocking your gas flow from the float bowl

    Again - you may want to verify fuel to the float bowl and out of the float bowl of each float bowl

    Why are you using Honda fuel line for your carb line? Is it the correct sizing and diameter?

    A lot of questions but all of us will need a little more info. On your responce you will need to address the front and rear carb independantly so we can see what is happening to each carb.
    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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    Just got done with a feeding/changing session and it is definately an extreme change....good so far, but very tiring.

    Travel'n that is a ton of questions, but here is what I have for answers

    The nozzles seem to flow clear to me, I have shot a bunch of cleaner through them and
    Wd40'd up the sliding section. Though I hadnt heard to grease it, I will try that.

    The Choke actuates good, though on return with my old lines I have to manually move up the rear on occasion. Most of the time it moves all the way up.

    The pistons move extremely smooth, though with the 20wt oil and new seals they are stiffer than when I bought the car and whatever fluid it previously contained. They clunk when they hit bottom. The centering nubs are still on the back carb, but not on the front.

    I have the plastic floats. I mentioned returning to the factory float valves. I am currently running the factory front float valve and the GP Sorenson Rebuild kit rear float valve. Set to 14.28 mm front and 12 mm rear. I ground down a bolt to the proper length and set the valve to close at the point of contact. THis is with me blowing air through the lines and the float held right side up. I am just a little high on the back right now...closer to 25 than 22mm in the sight tube.

    The car generally idles pretty smooth as is, even if the rear cylinders are doing most of the work. It only gets crappy when I lift the rear piston all the way up. And even then it doesn't die if it is warmed up.

    There is fuel coming out of each line and close to the height of the nozzle.

    I picked up the honda fuel line as motorcycle shops were mentioned as a source and this stuff is supposed to be non-hardening. Also, it was cheap and as close to home as autozone. The inner diameter is really close to the replacement lines in the rebuild kit. Just a bit over in fact.

    I think I have hit everything there is so far. I don't have any way to check my fuel pressure just yet, but that can be changed shortly. I have a low pressure electric fuel pump I may plumb in temporarily to see if that eases any of the problems. I think it maxes out at 5 psi.

    Here are the requested pics and a baby for good measure











    Thanks for your help
    Last edited by hogie; 05-11-2010 at 09:39 PM.

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    A picture is worth a 1,000 words. OK, a few things here.

    First and foremost, cute baby.

    Second. The hose from the float bowl to the nozzle is incorrect. It's also pinched on the front carb (4th picture) and that will restrict flow. There is a thin-walled, pre-shaped hose that goes there. It is available from ZT.

    Third. The "hanging nozzle" is a problem. It could indicate a) the need for grease on the nozzle, or b) a poor needle/nozzle fit. Use a liberal about of white grease on the nozzle and reinstall it (without the hose attached and choke arm attached). Work it up and down and ensure that it moves freely. Hold it in the up position and ensure that the piston is moving freely. Once you know that you have a good fit, attached the choke arm and run through the movement again. Then attach the fuel hose and do a final run-through.

    Lastly, What kind of headers are those and do you like them? I'm looking for headers myself, especially ones coated like yours.

    This is a lot of work, but a lot more fun then an extreme diaper change
    Gary
    Guardian of HLS30-91415
    Previous Owner of a 10/70 240Z ('83-'85)

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    They came with the car so I am not positive on this, but I think they are from MSA. Almost all of the receipts came from them, though I couldnt find the one with the header listed. They had a sticker marked made in mexico, but that has burnt off sometime in the last few months. It mounted up to the MSA premium exhaust without much fuss and sounds really good to me. Though, I really haven't gotten to drive it with everything working right.

    I will change out the fuel line and grease everything up real good tonight. Hopefully that will prevent me from doing the full tear down.

    You are right about the diaper changes though. I have no clue how he can completely fill a diaper the second you change him. That and pee on the wall and myself again two minutes later.

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    Registered User Gary in NJ's Avatar
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    You need to learn the "cover the penis" procedure. If you're not actively wiping something, let the open diaper flap over the 'lil fire hose.
    Gary
    Guardian of HLS30-91415
    Previous Owner of a 10/70 240Z ('83-'85)

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    Quote Originally Posted by hogie View Post
    .

    You are right about the diaper changes though. I have no clue how he can completely fill a diaper the second you change him. That and pee on the wall and myself again two minutes later.
    The joys of fatherhood!! A lot more of great memories just a fingersnap away! Enjoy them all!

    Great advise on the nozzles with the above post - keep us posted on your results
    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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    Well, I replaced the fuel lines, disconnected the choked, lubed up the nozzles, and I re-set the needles to seat of the piston. And the results are it will idle quite smoothly at 750 and the 1000 rpm mentioned earlier.

    If I cut gas to either carb it will idle roughly, but will carry on no problems. Using the bean dip method I get a rough idle when lifting either piston. When using the the lift pins the idle raises a tiny bit and comes back down on the front carb. The back just drops a bit in rpm, but it doesnt die.

    The rental fuel pressure gauge isnt detailed enough to really say, but it hovers right around 3 psi. I will probaly go ahead and toss that electric pump I have on. However, I will be grabbing a ford cutoff switch before I do that.

    Here is a video, thought the quality isnt all that great. Thanks for your help everyone.


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    Have you driven the car?
    Do you have any lean pops?
    Did you check for gas leaks from the bowl to the nozzle?
    Make sure you do not block your bowl vents - did you blow through them when you had you bowl lids off to make sure they are not obstructed - you should have your vents hosed to your air breather once you put it back on.

    If you have driven the car do you have any hesitation at any rpm?
    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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    I will get a chance to drive it tommorow I got cut a little short tonight. I didn't get any lean pops tonight, though I had them earlier in the year when the floats where set way too low. Also, no leaks between the nozzle and bowl signifying too high of float either.

    The bowl vents are for sure unobstructed. I have the foam filters and have added fitting to the back to accept the overflow tubes as well as the gas tank recirc valve.

    I will be able to let you know tommorow about the rest.

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    I visited The Z Barn a couple of months ago and picked up a few odds and ends and Roger is a great help. One item I purchased is a year correct air breather with hardware (the gaskets were even in good shape). I use to have the same air filters as you currently do. Honestly - I have more power and the engine bay looks a lot better - the way the air intake is designed it's kinda like an early version of "cold air induction" pulling air from the front of the engine bay, instead of around my hot headers, plus, you get the built in air horns. I followed a few threads and restored the breather and it is working great.
    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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    Not a shabby idea, though it will fall somewhere after the radiator, water pump, and new seatbelts!

    I really don't the look of the el cheapos I have now and if they don't perform as well as stock why have them.

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    I too recently went back to the OEM airbox. The lawnmower pods didn't provide enough flow at low rpm.
    Gary
    Guardian of HLS30-91415
    Previous Owner of a 10/70 240Z ('83-'85)

  32. #32
    Registered User Travel'n Man's Avatar
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    Quote Originally Posted by hogie View Post
    Not a shabby idea, though it will fall somewhere after the radiator, water pump, and new seatbelts! .
    I removed my radiator and took it to a radiator repair shop - they rodded, boiled, and repaired it for $35. I gave it a nice fresh high temp paint job (not on the fins), and she is as good as new!! It's taken me about 3 years but I am closing in on my project list. I did replace my seat belts with the MSA belts last year. A lot safer than what I had, which was nothing. The drivers side rides up a little high for me but I don't think I can adjust it without putting spacers under the bolts for the seats, which I will not do.

    How did she drive with the carbs?
    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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    Well I have good news and bad news. I only got to put 3-4 miles on her before an unrelated problem developed. It pulls strong from idle and runs good up to 4500 rpm or so. I never got past 2nd gear when getting on it so I wasnt going too fast as I am not very far out of town. When cruising about it at 30-40 (guestimated) everything goes fine. It doesnt seem to pull too quick in third gear, but I have never ridden in any other 240 for a reference either.

    I did have a couple of hiccups. Once while accelerating and 3/4 throttle it fell on its face at around 2 grand and then picked back up. The other instance was pulling away slowy from a stop sign while turning right. It cut power, I clutched in and it didn't stall. Two seconds later it was driving fine again. No lean pops or anything. I am guessing the fuel pressure really was as low as the gauge showed.

    Unfortuneatly, something is wrong with my tranny or driveshaft. I was cruising at a steady speed in 2nd and went to 3rd slowy. At which point I heard a whirring, sliding sound coming from the transmission. A second later it felt like the rear of the car was binding and vibrating real bad. So I clutched in and slowed to a stop.

    I couldnt see anything wrong and was in a bad spot on the road so I backed into a turn around. Once I went back to reverse the noise/vibration went away and I limped back home in first and 2nd. When I tried to go into 3rd a second time the same thing happened. I know 3rd isnt blown out as I used it when I first left the house. Perhaps something backed loose, but I have no clue what is causing it. The only other symptom is that I get a funny chirp sound almost like a belt squeel when I get off of the gas and stay in gear. It is extremely short in duration and may not be related.

    The only thing that I can think of is my drive shaft is shoved pretty far into the tranny. I had an extremely hard time fitting it into the car. The Ujoints are newish and as of two months ago the tranny was full of fluid. I am at a loss on this one, but at least the engine runs nicely now!

    here is the thread where I was having the driveshaft problems. http://www.classiczcars.com/forums/s...ad.php?t=34661
    Last edited by hogie; 05-13-2010 at 08:42 PM.

  34. #34
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    Wow - when it rains it pours.

    Have you changed your fuel filter?
    How did you sync your carbs?
    When she fell on her face are you sure you did not hear a carb backfire (or lean pop).

    It sounds like it is either your floats are still to low or your pressue is not correct - I know you previous post showed your pressure low so that may need to be your first fix - how are your rubber fuel lines? Are they the correct size? You may need to enrichen one or both carbs a little more.

    I think I would go back to your past thread and put your challange in there and see what feedback you get.
    Last edited by Travel'n Man; 05-14-2010 at 04:07 AM.
    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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    I changed the fuel filter before I started to try getting her running. So it is pretty new, but at 4 dollars also a cheap replacement. The metal lines were full of crud when I got her, so I blew those out with a ton of compressed air. Though I think I tried to run the original fuel filter a little after that to catch anything broken loose.

    My fuel tank is in beautiful shape and was quite shiny on the inside. There are new 5/16 outlet and 1/4 return lines hooked up. The main change is that I got rid of the vapor tank.

    I don't remember hearing any thing out of the ordinary other than it just cutting power. When I had lean pops while trying to get it tuned up they either extremely loud or no worse than a sneeze. My exhaust could have covered up a quiet one.

    I am going to check for any loose bolts tonight ande see if I can't up enrichen the mix a bit more. Thanks again

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    I synced the carbs at idle and at 2k with my unisyn.

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    Argh, I think the transmission is toast...I jacked the car up and ran it through the gears at idle. 1rst and 2nd no problem. As soon as I hit 3 it sounds like crap. Fourth sounds even worse and vibrates even more. 5th just pops right out as soon as the clutch is released.

    Also, after my extremely short drive last night the tranny was quite warm. Any one else agree that it sounds blown? I had a hardbody 5spd crap out once and it sounded like gravel was running through it.

    I have 3 transmissions in the attic to hopefully one of them is good...in fact one is marked 77 good in Junk yard paint on the top. Too bad I think they are all four speeds. I havent found any good ways to tell them apart externally. They all have L6 on the side with the B type shifter and a #6 towards the tail end.

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