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Thread: What Are the Weak Points of the 260z (for Endurance Racing)?

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    Sopwith21 sopwith21's Avatar
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    Default What Are the Weak Points of the 260z (for Endurance Racing)?

    Here's what we have:
    • 1974 260z early production
    • 1983 L28, N42 head
    • Not sure if we have an R200 or 180, but it's a live axle (welded diff)
    • Coilovers
    • Crummy stock brakes soon to be replaced
    • Close ratio 5-speed

    Hi guys;

    For some years we've raced our 260z on off weekends at local and regional club events with some success, winning 21% of our events. But now we want to take the same car endurance racing in long distance events and that's a whole new ball game. So the million dollar question is...

    What weaknesses does this car have that should be addressed prior to an endurance race?

    These are the problem areas we've had with this car so far:

    1. Occasional broken half shaft
    2. Dead ignition module every few races
    3. Weak 5th gear that we're afraid to actually use in a race


    If I pick up one extra half shaft, will the same one work for either side?

    Is there anything we can do to permanently fix the recurring ignition module failures?

    What else fails on these cars, and how should we prepare for it?

    Many thanks for all your thoughts!
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    Registered User 5150 will's Avatar
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    I'm not personally aware of endurance issues, but there are some guys that run a Z out of the Northwest (Washington or Oregon I believe). They have run all of the 25 hours of Thunderhill races and they have over 10k race miles on their car. The thing is typically like the energizer bunny so they know whats what with the endurance end of the Z. I believe they go by "C note racing" in the IRDC and NASA. They would definitely be the people to contact.
    Last edited by 5150 will; 12-31-2010 at 07:38 PM. Reason: add on info

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    Design wise not a whole lot. I know that some people in the 70's ran a front bearing oiler system, that was very rare.

    My biggest concern would be age with metal fatigue. 35+ year metal that has bent and flexed and vibrated, then put it under 20-24 hours of hell sounds like a potential for failure. So I'd check the metal.

    The car isn't as convertible for racing as some newer car so anything that can be done to reduce driver fatigue would be smart.

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    Stub axles, I would venture to guess. Maybe get a set of billet ones from MMS. Do the rules allow you to modify or upgrade the ignition system in any way? If so there are dozens of systems that can be more reliable. Get rid of the welded diff and get a good LSD unit in the car. The welded unit could be helping to tear up axles. Quaiffe comes to mind. A locked diff might make it push on corner entry as well.
    Last edited by cygnusx1; 12-31-2010 at 09:33 PM.
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    We've never opened the rear end of this car, so give me some basics... do we want the 180 or 200? Do all 200's come as LSD's?
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    Will is correct C Note Racing is their name and they run a lot, if you can contact them the guy who owns the car is Manfred. Sorry I don't have his contact details. I helped them with the 25 Hours of Thunderhill this year. Problems they had this year included alternator failures, chewing through alternator belts and a Broken Rear Diff Mount. Their alternator was a high output one, especially for when running the lights at night.

    You could also call Les at Classic Datsun he deals with a lot of Datsun vintage racing customers and probably knows the weak points better than anyone.

    I would say from what I have seen:
    • Half shafts
    • Stub axles
    • Diff mount
    • Extra alternators


    I also believe there was a post on here or hybridz about spares needed for 240Z most is probably valid for a 260Z.

    You probably have done it already but I would try to track down what is causing the ignition module failures, maybe changing the mounting location or grounding is causing the problem? I have no experience with those problems.
    Cheers

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    Get yourself an R200 if you don't already have one. I am not sure if the 260's are setup with the 180 or the 200. My 260 specific knowledge is weak. If it's a 180, you need to get appropriate axles and stub shafts to switch to the 200. All Datsun R200's are open diffs with much stronger spider gears than found in the R180. There are internals you can swap to make the R200 into an LSD. Search OBX, Quaiffe, or you can track down a Nissan R200 LSD which came in one very specific model year turbo 300ZX (1986?), white in color. You can also convert to an Infinity Q45 LSD rear end with more custom work. A must, as mentioned above, is to replace the front diff mount with an engineered RT style mount, or a solid mount.

    Oh, and one more thing, left and right axles are not interchangeable, as far as I know, due to lengths.

    Search over at HybridZ.org for all the terms and acronyms I mentioned here.
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    Yes, all 260 (coupe's) came stock with R180 diffs and yes, we did break ours in LeMons endurance racing. You will also need a R200 mustache bar to make the swap.

    You can use the short side half shaft on either side if needed, but it's best to have both and mark them. There isn't much length difference.

    Which distributor do you have? We have had stock ignition modules fail. We borrowed Geezer's ZX dizzy and module and we plan to swap once I buy one. Those too are know to fail often, so I'm not sure what the best long-term solution is.

    I've been told that the trans should be double roll pinned, but we haven't had a problem with our stock trans(s). We did break a trans housing when the R180 diff broke. The vibration and shock cracked the housing that holds the rear seal.
    Last edited by Jeff G 78; 01-02-2011 at 09:07 AM. Reason: Added info
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    '71 240Z, '78 280Z jmark's Avatar
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    Gira races an ITS 240Z in the SCCA endurance races. He can advise you.
    Mark
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    Pertonix and an MSD box will fix that dizzy issue for good. Then megasquirt if you plan on EFI.

    Where are you driving that you need 5th gear??? In the past 7 yrs I have had our 240 in 5th maybe a dozen times at best. With the current engine (185hp@rwhs) we topped out at 135mph. The new engine will add another 50 rwhp so maybe we'll get into 5th more often.

    By close ratio do you mean a 280b tranny? If yes, then fill w/ half Swepco and and ATF.

    Remove welded diff, get LSD or Quaife (3:90 gears for all around track use). Install RT mount. Replace 1/2 shafts w/ZXT CVs and 280 stub axles.

    Z31 calipers and Porterfield pads in front, Porterfield shoes in the rear.

    Engine cooling and oil pressure are your best friend. Plan accordingly.

    Please provide more info on your car's specs.
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    Sopwith21 sopwith21's Avatar
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    Very helpful, guys. Keeping notes on everything. Keep it going. Tx!

    Quote Originally Posted by gnosez View Post
    Pertonix and an MSD box will fix that dizzy issue for good.
    Already have the MSD box linked to standard ignition. Of course, that may be the electronic equivalent of pushing a bowling ball through a straw, but we're halfway there.

    Where are you driving that you need 5th gear???
    We're not. The question is whether to use the close ratio 5-speed and risk a missed shift and blowing the tranny, or use the 4-speed with the wider ratio and eliminate the concern over missed shifts.

    By close ratio do you mean a 280b tranny? If yes, then fill w/ half Swepco and and ATF.
    Never heard of a "280 lb" tranny. I'm talking about the close ratio 5-speed that had a smaller gap between 2nd and 3rd. Used on ZX's from - I think - 75 onward.

    Z31 calipers and Porterfield pads in front, Porterfield shoes in the rear.
    Already using Porterfields. The caliper change must be the key.


    Please provide more info on your car's specs.
    Next post. Tx again.
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    Additional notes:

    Triple SU carbs. Was cutting out in left hand corners at the last race. Hmm. Holley Blue fuel pump. Will send carbs in for service, including bigger jets, and replace all rubber fuel lines.

    New engine. Two races on it. L28 with N42 head, +.030, 11.9:1. Ran hot until we poured tons of fuel into it. Now it peaks around 230 degrees in a 30 minute event in 65-degree weather. I'm still worried about long distance races.

    15x9 wheels with Hoosier DOT's. Good combo so far.

    Stock brakes. Porterfield pads. Upgrade already planned.

    Suspension is good. Coilovers and Tokicos. 350 lbs in front, 250 lbs in rear. Handles very nicely. Slight push in, loose off, due to live axle.
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    Well first I suggest you spend the next week or two researching Zs and all related racing info. If you don't know what a "b" tranny is then you need to do some catching up.

    So here's a freebie - there are a number of 5-spds but for most people they break down into a few simple types;
    1) 77-79 "a"
    2) 80-83 "b" - for me there is a subset for the '80 tranny which I prefer
    3) turbo BW
    4) Z32 w/adapter plate
    5) truck, SX and others

    All this info and more is out there. Spend some quality time getting up to speed (no pun intended) and then ask more detailed questions. Most of the things you want can be found a click or two away.
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    '72 240Z(G) 3.2L
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    Triple SUs? Okay. What fuel pressure? Is 230 the coolant temp? If yes you have issues.

    We have run for nearly 6 hrs with only refueling stops and not overheated our 240.
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    Quote Originally Posted by gnosez View Post
    Well first I suggest you spend the next week or two researching Zs and all related racing info. If you don't know what a "b" tranny is then you need to do some catching up.
    I misread your post... thought you typed "lb."

    I didn't put the tranny in but can find out if it's an early or late edition. I'm sure it's not a Borg Warner.

    Either way, the question still remains. I would think that the 4-speed would be preferable to an early 5-speed, but the B 5-speed would be preferable over the 4-speed.
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    Quote Originally Posted by gnosez View Post
    Triple SUs?
    Yes.

    What fuel pressure?
    Dunno yet.

    Is 230 the coolant temp?
    Yes. Temps were awful until we dumped a lot more fuel into it. Now it peaks at 230, rides around 220-225. Would sure like to drop 20 degrees or so.
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    Quote Originally Posted by gnosez View Post
    Remove welded diff, get LSD or Quaife (3:90 gears for all around track use). Install RT mount. Replace 1/2 shafts w/ZXT CVs and 280 stub axles.
    Speaking from experience, a Quaife WITHOUT a cooler will lead to trouble. My R200 without one was hitting 300 degrees at the end of a 1/2 hour session.

    No experience with a welded, but I'd venture to guess it would operate a bit cooler. The flip side is it does put additional strain on the halfshafts - the only time I'd hear about guys breaking them was with a welded diff.

    Quote Originally Posted by gnosez View Post
    By close ratio do you mean a 280b tranny? If yes, then fill w/ half Swepco and and ATF.
    2nd on the ATF/swepco, my synchros were getting a bit tired, this cleared up the grinding immediately, and the shifts were quicker too.

    Quote Originally Posted by gnosez View Post
    So here's a freebie - there are a number of 5-spds but for most people they break down into a few simple types;
    1) 77-79 "a"
    2) 80-83 "b" - for me there is a subset for the '80 tranny which I prefer
    Technically both the 77-79 and 80-83 5spds are "b" transmissions, all fs5w71b's. I ranted about this on the transmission/diff setup thread. While yes, 2-3 is a bit closer on the 80-83, for all practical purposes 1-4 on both the 4sp and 5sp (77-83) are the same. You're not going to see any big difference until you go with something like an option 2 comp box or ratios similar to that. The only time I'm going slow enough to use 2nd is at race starts or with lapped traffic.
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    Quote Originally Posted by Jeff G 78 View Post
    I've been told that the trans should be double roll pinned, but we haven't had a problem with our stock trans(s).
    This has been discussed at length on other threads. IMO it's really for the most ham-fisted drivers. Many speculate the actual problem is the pins "walk" out of the forks and some guys actually safety wire them in place.
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    Marooned Fish cygnusx1's Avatar
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    As for cooling, you may want to take a look at the aerodynamics section at hybridz as well. There are basic aero tricks that a racing S30 should have. Some of which relate to cooling.
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    Most of the aero tips can't be used in SCCA or vintage racing sad to say. We just removed the MSA Type II airdam, the blocked off grill areas, the radiator shroud, etc. to make our 240 fit VRG and SVRA rules.
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    Suspension is good. Coilovers and Tokicos. 350 lbs in front, 250 lbs in rear. Handles very nicely. Slight push in, loose off, due to live axle.
    OK... you don't have a live axle, you have a welded diff. Live Axle is what's under 1970s Chevy pickup trucks. You front Tokico shocks (unless they are HTS shocks) are junk by now with those spring rates.

    Shoot for a constant 200 degree coolant temp on the track. Oil temps should be around 230 to 250 with synthetics. If you don't already have an oil cooler, put one on immediately. Stick with the R180 diff and run a real limited slip unit. Add a diff cooler if you're running sessions over 1/2 hour. For anything over an hour you'll probably need a trans cooler - depending on how hot it gets where you race. Redline MT90 in the trans and 80W/140 in the diff.

    Get rid of the Porterfield brake pads and move up to at least Hawk Blues. Get as much air to the front rotors as possible (two 3" ducts are best, one to the caliper and one to the rotor).

    Keeping a car alive in an endurance racing is mostly about heat management (coolant, engine oil, trans and diff oil, brakes, driver comfort, and tires.)

    For spares you should bring one of everything and, if possible, four completely assembled suspension corners. You'll need the equipment to do complete oil and fluid changes, brake bleeding, caliper and rotor swaps, and draining the fuel cell without spilling a drop.

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    Quote Originally Posted by gnosez View Post
    Replace 1/2 shafts w/ZXT CVs and 280 stub axles.
    I have a couple questions about swapping stub axles.

    1. The OP said he has a 260Z - looking at the parts catalogs - it seems that the 260Z and 280Z got the same stub axles to begin with - after 08/73 {yes/no??}

    2. The original 240Z stub axles - mounted in the strut housing - with a spacer {size A, B, C} and washers at each end of the spacer - between the inner and outer bearings. It seems that the 260Z and 280Z stub axles still use the spacer {A, B, C} but without the washers on each end.

    So the question is - if you swap to the 280Z stub axles into the strut housings machined for the 240Z set up - do you have to use the washers or not?? Put another way - is there a difference in the machining or build of the strut housing - where the stub axles mount - between the 240Z and 280Z struts? {not talking about strut tube thickness}.

    I'm trying to rebuild a set of 73 rear struts - the previous shop took the stub axles out - and it seems they lost the washers that go on each side of the spacer. Looks like I could just get a set of 280Z stub axles and use them without the washers. {the washers are NLA}.

    FWIW,
    Carl B.

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    The point of the distance piece (spacer) and washers are to end up with end play and rotational torque with the specs listed in the FSM. Generally the spacer goes with the hub so in the 280Z, MM stub axles installs I've done in 240Z hubs, I assemble with the 240Z spacer and no washers and then torque to 175 ft. lbs. I then measure end play and turning torque. If they are within spec then I'm done.

    If the end play is out of spec, I increase torque in 10 lb. increments until the end play is within spec or I reach the max torque number listed in the FSM. If I reach the max torque spec I go with the next shorter distance piece and try again. I've had to do this only once in the last 8 years

    If the turning torque is too high I disassemble and add one new copper washer between the inner bearing and the spacer. Then re-torque to 175 ft. lbs. and check again. I've never had to add more then one washer and that is only needed in about 20% of the assemblies I've done.

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    Quote Originally Posted by John Coffey View Post
    You front Tokico shocks (unless they are HTS shocks) are junk by now with those spring rates.
    You could be right, but the suspension was not a random design. Pro Shocks of Lawrenceville, GA specializes in racing suspensions and they did the work. Of course, that doesn't make them perfect... but in late October we ran the quickest lap the car has run since the summer of 04 and finished 1st and 2nd in our events, so they must have done something right. Very slight push in, slightly loose off. Perfectly balanced in the center with good weight transfer and constant, predictable and controllable handling at the limit. I'm all for making it better, but the 19 cars we beat that weekend unanimously agreed that it's not junk.

    Shoot for a constant 200 degree coolant temp on the track. Oil temps should be around 230 to 250 with synthetics. If you don't already have an oil cooler, put one on immediately. Stick with the R180 diff and run a real limited slip unit. Add a diff cooler if you're running sessions over 1/2 hour. For anything over an hour you'll probably need a trans cooler - depending on how hot it gets where you race. Redline MT90 in the trans and 80W/140 in the diff.
    Good thought on the diff cooler. Oil cooler is already in the plan. And thanks for the temperature levels and fluid recommendations - we'll use them.

    Get rid of the Porterfield brake pads and move up to at least Hawk Blues. Get as much air to the front rotors as possible (two 3" ducts are best, one to the caliper and one to the rotor).
    Already ducting 4 inches through both headlight holes to no avail. We'll look at the Hawk Blues upgrade, but I don't think anything short of a serious system upgrade is going to do the trick.

    Granted, we were running a very tight track that's murder on brakes, but we were boiling fluid within 20 miles of racing. And it's not the driver. I think I'm going to follow your advice on the pads and the previous advice on new rotors/calipers as well. It's a total system upgrade, I'm afraid.

    Keeping a car alive in an endurance racing is mostly about heat management (coolant, engine oil, trans and diff oil, brakes, driver comfort, and tires.)
    Excellent way to put it. Good thoughts. Thanks!
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    Thank-you John, that is very helpful.


    Carl B.

  26. #26
    Crumudgeon
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    Quote Originally Posted by sopwith21 View Post
    You could be right, but the suspension was not a random design. Pro Shocks of Lawrenceville, GA specializes in racing suspensions and they did the work. Of course, that doesn't make them perfect... but in late October we ran the quickest lap the car has run since the summer of 04 and finished 1st and 2nd in our events, so they must have done something right. Very slight push in, slightly loose off. Perfectly balanced in the center with good weight transfer and constant, predictable and controllable handling at the limit. I'm all for making it better, but the 19 cars we beat that weekend unanimously agreed that it's not junk.
    I didn't say your car or its performance was junk. If your front shocks are Tokico Illuminas (BZ3099 - typical shortened 240Z fronts) then Tokico's engineers and my own personal experience says the rebound valving is gone with springs rates of 350 lb. in. There may be a different Tokico shock in there that have the correct rebound valving for the spring rate. The only two Tokico shock inserts that I'm aware of that can handle those spring rates are the HTS102F and HTS112F.

  27. #27
    Sopwith21 sopwith21's Avatar
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    I agree! My only point was that they appear to still be working. And yes, they are BZ3099's. But if the rebound is shot, I should be having rebound problems under acceleration out of a turn. I'm pretty experienced and can't feel any such problem???
    2013 Mid-American Oktoberfest Winner - 2013 COMMA Challenge podium - 2012 ARCA Truck Series -
    2012 Super Cup Series Podium - Official test team for the Mitsubishi Evolution - 2010 GT Challenge Winner -
    2005 COMMA Challenge polesitter - 2004 GT Challenge Series champion - 2004 COMMA Rookie of the Year -
    2003 HMRC winner - 2002 GT-2 winner - 2001 GT Challenge Series winner - 2000 CARS series winner -
    2000 Winchester Speedway polesitter - 1999 Lucas Oil Raceway winner

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    Registered User rxsleeper's Avatar
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    Here are some pictures of my brake setup. 2 3" lines to each shroud. Excuse the dryer duct, this was done by the previous owner and has been corrected. FWIW, I run hawk HT-10 brakes in front, and OEM drums in the rear with carbotech shoes. My brakes don't work well until I get several laps on them in a session/race but then work very well, for even the longer races. I do burn out the caliper seals after about 2 races. I check them after every race and rebuild/replace the calipers as needed.

    JohnC said it best. The only people that are breaking stubs are usually running a welded diff. I haven't broke one yet but I recently picked up a quaife and I am still looking for a clutch LSD (R-180).

    Heat management is the key. Redline in the gearbox and diff. Coolers for engine oil and if legal for your class the diff. I have only had problems with engine cooling when a thermostat failed closed.

    Now for the pictures:






    A better picture of my current set up





    FWIW, this setup was used on my car to win several endurance races on the "left" coast before the car migrated East
    Last edited by rxsleeper; 01-04-2011 at 07:42 AM.

  29. #29
    Crumudgeon
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    Quote Originally Posted by sopwith21 View Post
    I agree! My only point was that they appear to still be working. And yes, they are BZ3099's. But if the rebound is shot, I should be having rebound problems under acceleration out of a turn. I'm pretty experienced and can't feel any such problem???
    Rebound issues are generally felt on corner entry and mid-corner. The car turns in well but "falls" over on the outside front shock, doesn't take a set, and then understeers. On corner exit you should see more weight transfer to the rear and understeer.

    Your shock may be fine, there are exceptions to every rule, but keep an eye on it. It may not leak any oil and still have problems with the rebound valving. What setting do you run the front shocks at?

  30. #30
    Motorsport z-spec's Avatar
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    Verry interesting hear technical things about racing Z,s there should be much more written about this .

    I run a 4.40 R180 from a Subaru WRX Gr N Rally car , this is a purpose build Plate type LSD diff from Prodrive Subaru STI , we made our own output flanges for the Datsun drive shaft .
    I have a 200SX gearbox with a 240Z Bellhouse , fits straith to a L6 engine , with better gearshift and close ratio 2.43-1.81-1.36-1.00-0.82 (Kameari gear kit )
    My second option would be a Turbo T5 with a G-Force Close Ratio kit these have more options for 5e gear

    For brakes we use the Toyota 4 pot Calipers or the much lighter AP Racing
    I do not have expierece with Datsun 240Z in Endurance racing but i have with my 65 Shelby Mustang with Spa 6 Hour and Nurburgring 500 Marathon
    We uses yellow Pagid but I prefere Performance Friction , they are easyer to bedding in and frienlyer for the Discs , the rear drums we use Porterfield R4 but the only the racing stuff the other stuff dont last for 6 hours.

    Whats actually the minimum weight you can build a Racing Z
    Adrian
    1/1970 240z HLS30-01639
    8/1970 240z HLS30-07996
    8/1970 240z HLS30-07998
    8/1970 240z HLS30-08449
    www.va-motorsport.com

  31. #31
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    Quote Originally Posted by z-spec View Post
    Whats actually the minimum weight you can build a Racing Z
    Depends on which class/sanctioning body and class you are racing with. In my case, I must weigh not less than 2430 at the end of the race. Last time I rolled over the scales (including my fat butt at 200+ lbs ) I was at 2437 and I had about 2 gallons of fuel left in the cell. I have a friend with a tube frame Z that weighs around 1900 lbs and he still has a lot of steel body panels. He adds ballast to make minimum weight.

    Paul

  32. #32
    Sopwith21 sopwith21's Avatar
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    Quote Originally Posted by John Coffey View Post
    Rebound issues are generally felt on corner entry and mid-corner. The car turns in well but "falls" over on the outside front shock, doesn't take a set, and then understeers. On corner exit you should see more weight transfer to the rear and understeer.
    We're not getting any of that. The car turns in with slight understeer, then sets and balances in the center quite well, then slowly and predictably transfers weight and slightly oversteers coming off the corner. Everything you would expect with a welded diff. The car does not snap from under to over steer. It's slow and predictable.

    Your shock may be fine, there are exceptions to every rule, but keep an eye on it. It may not leak any oil and still have problems with the rebound valving. What setting do you run the front shocks at?
    I will, thanks. And now I know what to look for. We set the fronts at 3 and the rears at 2. We've tested them at all settings and this seems to work best on a technical course that averages right at 75 mph.

    I suppose we could change the settings to something more extreme, but if you have to go 5 at one end of the car and 1 at the other, to me that's just indicative of another problem somewhere else on the car. I don't think you can over-adjust struts to compensate for another issue... we just need to solve the root problem to begin with and let the struts do their job. So 3 and 2 seem to work okay.
    Last edited by sopwith21; 01-04-2011 at 01:51 PM.
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    Quote Originally Posted by z-spec View Post
    Verry interesting hear technical things about racing Z,s there should be much more written about this .
    http://www.hybridz.org

  34. #34
    Sopwith21 sopwith21's Avatar
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    We're at 2,213 lbs and legal.
    2013 Mid-American Oktoberfest Winner - 2013 COMMA Challenge podium - 2012 ARCA Truck Series -
    2012 Super Cup Series Podium - Official test team for the Mitsubishi Evolution - 2010 GT Challenge Winner -
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  35. #35
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    Is your airdam deforming in your avatar picture?? Urethane?
    if a little knowledge can make you dangerous, I'm a little dangerous

  36. #36
    Sopwith21 sopwith21's Avatar
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    Yes, but not due to airflow. When it was originally installed by another owner, it sagged in the center. We tried to bolt it up again after the plastic had developed a memory and it deformed it a bit.
    2013 Mid-American Oktoberfest Winner - 2013 COMMA Challenge podium - 2012 ARCA Truck Series -
    2012 Super Cup Series Podium - Official test team for the Mitsubishi Evolution - 2010 GT Challenge Winner -
    2005 COMMA Challenge polesitter - 2004 GT Challenge Series champion - 2004 COMMA Rookie of the Year -
    2003 HMRC winner - 2002 GT-2 winner - 2001 GT Challenge Series winner - 2000 CARS series winner -
    2000 Winchester Speedway polesitter - 1999 Lucas Oil Raceway winner

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