anesthes

OK..

Someone.. Had done a swap to a ZF6, and used a 4+3 singlemass flywheel. Someone also has stated that the "longer ZR1 stud is needed because the singlemass flywheel is thinner than the dual mass".

I spoke to CentralCoaster. He doesn't know. He said he hasn't tried the ZR1 stud.

So before I go and BUY A STUD, since I need one anyway mine is stripped.
WHO has done this swap, and what stud did you use, or specifically, has anyone had success with the ZR1 stud or did it make the slave cylinder travel too far?

I want to hear from a guy (or girl) who has DONE it. Because I found 50 billion threads with "you need to" but they were all written by guys who hasn't "Done it" so I can't decipher the myths from the facts.


-- Joe

RandyJ75

Check w/Larry, LD85.

Zix

Give Bill at www.zfdoc.com a call, he's done a couple of those swaps recently and should be able to give you the info you need. Also, he's probably still up and working right now!

96GS#007

Most use the Camaro flywheel. It needs to be machined .090".

LD85

I've never used the ZR1 Stud/4+3 FW combo.


FWIW, the ZF geometry and dimensional stack ups are so sensitive, that I gave up on the ZF stuff parts. Plus you a re limited to certain expensive clutch components.

I know how to make it work as well or better without the ZF parts so I don't use them


Essentially, I use a 4+3 FW , PP and Disc, .100" spacer between the BH and Block, and a Hydraulic Howe Push Type slip on TOB, a Wilwood 3/4" bore Master Cylinder, and a Clutch Pedal travel stop.

Believe it or not, the BMW's use a Pedal Stop as well.

anesthes

This is probably the exact setup I'm going to go to next fall, but I wanted to try the swap with "known singlemass replacement" but half way in I find that 90% of the posts are by folks who have not even done it, and when I get told to ask someone who has done it (like you) I find out that person actually did it differently.

-- Joe

anesthes

Hello,

Why does it have to be machined .090" ? I'm assuming the LT1 for T56 flywheel is .090" thicker than the ZF6 dual mass, and the clutch fork will crash into the BH ?

-- Joe

VanSpeed

Joe,

Here is what I did. This doesn't answer your question on the 4+3FW/Push type clutch, but gives you an example of what can work.

When I swapped to the ZF 6 speed in my 85 4+3 I used a Fidanza aluminum flywheel that was specifically made for the older 2 piece rear main seal blocks and the stock ZF clutch set up (non ZR1).

With this flywheel I used the stock pull type ZF clutch, shorter L98/LT1/LT4 pivot stud, later LT1/LT4 magnesium bell housing, and later LT1/LT4 clutch master cylinder and slave cylinder. It is also possible to use the earlier L98/LT1 aluminum bell housing, it depends on what you want to use and what starter you want to use (the earlier bell housing uses the large nose starter and the later magnesium bell housing uses the small nose starter).

Just remember the clutch (it’s really just the throwout bearing) has to match the year of your transmission, early black tag or later blue tag because the throwout bearings have a different ID size.

If your 87 has the one piece rear main seal then you can use the stock ZF dual mass flywheel or an after market single mass steel or aluminum flywheel for the ZF 6 speed Corvette, more choices.

I do not have experience with the push type clutch conversion for the ZF but others have shared about doing this. I have 572 HP at the crank and use my car for track days and the set up I described above has been working just fine for my set up and car use.

Brian

anesthes

Brian,

I appreciate the response. I've compiled kinda a 'faq' on the ZF6 based on my measuring, and interviewing/talking with folks like yourself who have 'done it'.

http://members.cisdi.com/~anesthes/zf6/

Your aluminum flywheel which is a direct replacement for the dual mass is probably the same thickness as the dual mass it replaced. So it makes sense that you were able to use the stock pivot stud.

Central Coaster also used the stock pivot stud, and hes using a stock 4+3 flywheel thats even been shaved.

So the question is, has anyone actually used the ZR1 pivot stud or is it a myth? If you search, I see lots of advice to use one. But have yet to actually talk to a guy who did.

Thanks!

-- Joe

redrose

don't have a zf, don't want one, but fwiw, lakewood (see summitracing) sells an adjustable height pivot stud for abt $20.

No Go

Check my homepage for my results using the Camaro flywheel as 96GS#007 mentioned.

anesthes

Hi,

Yeah that seems pretty common. Pretty much direct from the FAQ. I'd have imaged more people though who have swapped from a 4+3 would have re-used the single mass flywheel. So far myself and Centralcoastar are the only ones I know of. So where does this ZR1 stud thing come from?


-- Joe

pablocruise

Hmmm...I never saw or heard of using a ZR-1 stud.
I got most of my info here.
Musta been 2001 or 2002 when I did my swap.

anesthes

http://forums.corvetteforum.com/show...ight=zr-1+stud
http://forums.corvetteforum.com/show...inglemass+stud

One guy says use it, then says don't use it. The idea seems to be floating around..

-- Joe

byebyeL98

I think that guy you are referring to is me. I don't believe I contradicted myself in either thread. In each case I pointed out that a short pivot ball stud needs to be used with an OEM dimension flywheel. The longer pivot ball stud is recommended for use with the thinner 4+3 flywheel, but as LD85 pointed out, the geometry and dimensional stack ups are VERY sensitive.

In the early stages of my swap, I was going to use my 4+3 flywheel and a longer pivot ball stud, as recommended by TPIS (I have a write up from them that I'll try to post later). Because the 4+3 flywheel will not work with a sprung clutch disc (and I wanted to go with a sprung disc), I went with an OEM dimension aluminum flywheel and back to the short pivot ball stud, so I can not fully verify whether or not the longer stud is actually needed for the 4+3 flywheel. You mentioned CC uses the shorter stud and a 4+3 flywheel, so it obviously can work that way, but I don't know what length bell housing he is using or if he is using a spacer between the engine block and bell housing. Little things like that DEFINITELY make a huge difference when tolerances are already so tight.

This weekend, I'll compare depth measurements of my original 4+3 flywheel with the OEM dimension aluminum flywheel and post results. I'll also compare the long pivot stud with the shorter stud as I have them, too .

anesthes

Who recommended it? I'm not pointing fingers, or saying you did anything. What i'm trying to do is solve this. I've yet to find someone who is using the ZR1 stud, and thats my issue. I need to figure this one out.

Interesting. So TPIS started this? So it must means on a car at one point in R&D, someone used the longer stud..

He's using a normal ZF6 bell housing, which measure 6 1/8" (6.1250"). It's the "deep" bell housing, that was on all L98/LT1 cars. There was an earlier revision ZF6 bell housing on 1989 cars which simply had a bigger starter hole.

Someone had told me there is another depth bell housing, a more shallow one which is supposedly 5.850" or something like that (for a ZR1 perhap?). So Say we have this shallow bell housing that's already nearly 1/4" closer to the flywheel, I can't see how a ZR1 pivot stud would help there. And since we know that central coaster is using a 4+3 flywheel (which was even resurfaced) with the 6 1/8" bell housing, and a normal length stud than we know that combination works. So I guess i'm even more stumped now as to why this ZR1 pivot stud is recommended.

For the love of god, I can't tell you how much i'd appreciate that. I can't find the measurements ANYWHERE on the pivot studs. I'd love to hear the difference in thickness of the flywheel too.

-- Joe

jadedvette

I swapped my 86' over a couple of years ago, it's not that bad. I used the lightened steel flywheel from GM that is for the 4+3 corvette, a camaro disc (Zoom Purple), ZF pressure plate and throw out bearing (Valeo) The longer stud, ZF master and slave cylinder, and line was used also. I didn't change the clutch pedal but I changed the bushing in it. It was well worth it. With the 4+3, sometimes I had OD, sometimes I didn't. Also installed the B&M Ripper (firm shifts).
Good luck, Joe

anesthes

You used a camaro disc with the 4+3 flywheel? I'm running the 16lbs 4+3 flywheel too, and I dont see how its possible for the sprung-hub camaro disc to fit??

Now I'm confused again!

-- Joe

j-stingray

i did actually use the fidanza ,stock clutch and and plate AND the ZR1 pivot stud it worked but a had to cut the belhousing up a little bit so i could slip the clutch fork on
worked fine but i overtightened the original bolts of the clutch:o :o
so i had to take it out again and now im driving with the original flywheel with a centerforce DF clutch & plate works fine to
but with the fidanza i really felt the revving difference

i also tried the 4+3 flywheel with a kevlar plate [with springs from TPIS] and original clutch
but had to take it out because i had unbalance beyond the 4500 rpm

greetzz jeff.

jadedvette

If I remember correctly, The ZF disc hits the pp bolts of the 4+3 flywheel, so the camaro disc is used. That advise and the longer stud came from McClod. I used their disc first (didn't last long).
Joe