Courtshark

Saw Sterling's revived thread about Spec 3+ clutch break in, and that couldn't be more on time for me. My clutch slips once the car is warm and only on hard acceleration, i.e. the fun times I'm getting on the bwwaaah pedal. That sucks! I want to go ahead and upgrade the clutch since I need to replace it anyway.

Spec 3+ is clearly overkill for my current set up; I do, however, intend to add more power, either a turbo system or a supercharger, within the next 2 years.

I basically never drive the car in traffic; only about 3k miles per year. So, what clutch package should I get? Should I upgrade the flywheel as well? If so, what are my options, and what are the best sources for clutches?

Thanks in advance.

Rob Edwards

If boost is in your future, then you're either going to be buying one of those Spec clutches, or modifying a DD clutch with a stronger PP. But I can tell you that the latter is slipping (and getting worse) at the torque maximum in 4th gear in my N/A stroker with only about 400 rwhp, after only about 5000 miles of hooning. I'd assume that Stage III Murfs and Twin Turbo 5-speeds (with a lot more power that me) are having the same problems with a DD clutch (?)

AFAIK AO and Tuomo's Spec clutches are still holding up ok (?)

Greg B is in the midst of working on a carbon clutch, parts are due in soon and I'll update when the install happens. Thread on it:

https://rennlist.com/forums/928-foru...-anyone-2.html

mark kibort

go stock clutch with a stiffer (slightly modified) pressure plate and be done with it.
Ive been racing mine for 3 years with 373rwhp and 420rwt with no slipping or issues what so ever, plus i still drive it on the street often.

racing clutches are a pain around town.

Rob Edwards

Perhaps if you tuned that thing you'd start having clutch troubles.

Tom. M

Just as an aside....My GT did this way back when I got it (only when warmed up)....thought it was a worn clutch too. Replaced the clutch with a stock one...and still had the same problem.

Ended up being a problem with the slave/master. The master would not come up in the bore enough to allow fluid from the brake reservoir to make it down to the slave. The fluid was essentially trapped between the master and slave. Worked fine when cold...but as the engine warmed up, the fluid did too (line runs right under the oil pan) and when the fluid got warm..it expanded..and actually made the slave push on the release arm thus causing the clutch to slip when hot.
There was a thick washer on top of the master piston that I removed and now I don't have a problem.

One way to check is to try and bleed the clutch at the slave (pressure bleeder up top). When I cracked the slave to bleed..it would just spit and not flow smoothly. Once the master piston had it's full travel back..bleeding was a breeze. You might also want to check to make sure the master is coming all the way up the bore...if air is trapped there..it won't move up enough to allow the fluid to come into the bore too..

good luck..

Courtshark

Thanks for the responses. I don't think I'm going to be super aggressive with my power-adders; famous last words, right? Aiming for 400 rwhp, but how to get there is still very much up in the air. Based on Mark's response, sounds like a stock clutch can handle that. How does one "slightly modify" the presure plate?

Rob Edwards

you send a DD PP and an 85-86 flywheel To Mark Anderson, who has a stronger diaphragm spring installed (and maybe stronger drive straps, I can't recall). Then (if you're going to retain stock brains for sharktuning) you need to have an S4 auto's timing ring installed on the 85-86 flywheel and tacked in place. Then they ned to be balanced together.

jcorenman

Yes, but how much torque?

Rob Edwards

Dunno, it's been 15 months since I installed the headers and haven't found time to get back to the dyno. Still need more ST'ing, too....

Whatever the number is, Anderson's modded DD PP isn't up to the task, though it's still ok for spinning tires in low gears (Ask Hans about his ride at SF11 )

The other thing about the DD setup in an S4+ is that the pedal effort becomes very light, too light IMO- makes it hard to modulate, even with the assist spring completely backed off.

Rod Underwood

I have two Spec 3 clutches and they both chatter at start up. They hold perfectly, but they are not fun to drive. I contacted Spec after the first one and they indicated that my fly wheel runout was more than .012, certainly NOT their problem, and so I checked the second one after it was resurfaced and it was .001 and it still chattered. I babied both for about 1000 miles and have just gotten used to driving them, but I'm not sure I would EVER put another one in.

Rod

mark kibort

probably near 400rwt too, even if it is 420rwt, as I have, the stock stuff , but stiffer, should be fine

as was said, anderson has a line into getting the pressure plates modified to be stiffere (stronger).

I dont know 420rwt is the norm for even a tuned one, but it would be more toruque up over 3500rpm too! 420rwt at 5200RPM would be 420HP, and that would be nice and the clutch still wouldnt slip, as that is torque based as you know.

anderson and fan started shreding clutches when they got up in the 500rwhp range, i think. Ive had great luck for years with the stock clutch discs. they can handle it, if you drive the car right. start burning the clutch up, drag racing, etc, and the stock stuff wont last i would imagine.

blown 87

Mine feels perfect.

GregBBRD

Completely different applications.

I'd guess that most everyone with increased horsepower drives their cars a bit harder on the street than Kibort drives his car on the track...which is why the stock clutch parts don't work for long, on high output street cars.

I think that Kibort has figured out methods of getting long life out of marginal pieces on the race track, by being uber smooth. I'm not saying that's a bad thing, just not the "norm". Mark avoids putting down the pedal hard enough to spin the rear tires....my customers actually like the feeling of doing this.

Jadz928

Mike,
I'd go with an early dual disk setup.
Lighter flywheel and lower rotating mass clutch pack = better throttle response (more 'blip' -able).

You'll find better performance gains going this route than getting a 'grabbier' clutch.

PS. I can't remember if I responded to you text. If not, sorry. Give me a call.... just chillin'

Happy New Year!

Courtshark

Happy new year everyone!

I like the idea of upgrading the flywheel. That made a huge difference on my modified SPG, while a super high performance puck clutch did not. Hated that disk, actually. Chattered like crazy.

GB's analysis makes sense, too. I'd like to think as smooth a driver as Mark... but then I wake up.