I have seen a number of you comment that the SPEC clutches come marked with the pressure plate to maintain balance. Does this marking occur at the SPEC factory or somewhere else? I am just trying to ascertain if I order the kit from an aftermarket supplier rather than SPEC do I still get the same balancing? Where is the best place to order from for these? Thanks.

--Calvin

 

a couple of the members have had some real issues with spec, have you thought of using a different clutch?

 

Huh? Other than my spec stage 2 kevlar which blew out the center after 12k im not aware of spec issues here. It also aruable that I was putting too much torque (530 rwtq on juice) through it.

Im happy w my spec stage 3+ clutch behind my blowerworks sc 93 vette. 500 rwhp/475 rwtq. It has lasted 20k miles and still engages as if its brand new.

That's what I hate about other clutch (oem, centerforce, etc.). You can feel them wear out. The clutch release point changes (as you are lifting up on the pedal), it gets higher on the pedal travel as it wears out.

I don't notice this on the spec.

I also don't know what other options you have out there. Mcleaod twin disk but they are expensive and very brutal on the drivetrain.

One piece of advice. The new throwout bearings (acdelco) seem to be made in china and are sloppy (lots of play). Be aware of this and you may even want to stay w your used stock oe one vs. The china junk. Your call.

 

the most recent thread was one by member "DR. Huxtable" , had some fit and manufactoring issues right out of the box. I'm just advising more research. theres other posts about it also

 

http://forums.corvetteforum.com/c4-tech-performance/2879552-dropped-the-zf-today-and-discovered-problem-yet-i-still-cant-get-it-fixed-help.html?highlight=spec+clutch http://forums.corvetteforum.com/c4-tech-performance/2879052-major-problem-at-the-end-of-my-build-please-help-me-i-cant-believe-this-is-happening.html?highlight=spec+clutch

 

Wasn't Dr huxtable's problem found out to be an improper clutch fork that was installed by the previous owner? I gathered from that post that Spec sent the right parts on the first try and the problem was on his end. It wasn't his fault but the previous owner did a booboo.

 

just did a search myself, running bout 60/40 in favor of the spec, lot of the issues have to do with installation, not all of them spec's fault, again , research is critical you are completely right, gunny, reread the huxtable post, had some pins in that caused issues also, seems his fix was either to tap them in further or remove them, again m ostly installation issues

 

So where did you guys buy your spec clutches from and did they come marked from a balancing perspective? Also, my throwout bearing was squeeling, which is why I pulled the thing to begin with - along with a knocking flywheel. So since I have to replace the flywheel I am not aware of many places that have clutches that bolt up to the SMF with the springs and retain the stock release mechanism other than SPEC. Anybody know where to get a non-Chinese TO bearing? Thanks.

 

on my LT4 engine with a stock lower end (let me emphasize stock) with all the original factory balance, the Spec lite weight billet steel flywheel and stage three plus clutch bolted in and performed without any balancing issues. to Spec I give a

 

for the non-chinese TO bearing... you can try to find a junked vette or something.

Yes, I would think you are better replacing your TO bearing with a USED USA built AC Delco unit vs. 'Made in China' AC Delco throw out bearing.

All this said, I had to use the chinese throwout bearing w/ my current spec stage 3+ and no issues yet.

However, the pedal didnt feel as tight (release point is higher off the floor) than it did when I put my old spec stage II clutch in with a new ACDElco Made In USA throwout bearing.

On a final note, stage 3+ is the clutch I recommend.

Stage 2 worked great until it blew up on me (busted center out of it while on a highway pull), stage 3 is a radical, fan blade looking 'puck' design clutch with poor streetability.

Stage 3+ is a sprung hub design with an OEM looking disk type design for good streetability (allows a tiny amount of slip when feathering the clutch) with great 'bite' still when you let the pedal out fast for performance driving.

I do not recommend a non-sprung hub clutch on our cars because they are too rough on the drivetrain / street. Also zf6 noise can be heard, from what I hear, without a sprung hub clutch.

Finally, drop the heavy 40 lb dual mass flywheel for an aluminum fidanza 12 lb flywheel to get rid of rotational intertia. I picked up a tiny amount of gear noise during hard acceleration, or if you lug it up a hill, but nothing objectionable. The key is to still have a sprung hub clutch and that will dampen gear noise.

 

To be quite truthful, I am planning on going with the stage 1. It provides >500 lb-ft of capability, which seems like plenty for me at high altitude, as I would have to be producing 600 ft-lbs at sea level which would be one hell of a radical engine. Almost all the hard use will be on a road course, with maybe 1 dragstrip trip a year. The stock clutch disc holds up to this so I would think the Stage 1 from spec should as well. After all, it is an 11" disc. Is it possible the spec discs are inferior to the OEM?

 

for me it wasnt the disc. In fact, right before my stage II clutch busted out the center, I was thinking how good of a disk it was.

meaning that the release point on the clutch pedal stayed consistent despite tons of road racing, hard street driving / shifting, peel-outs, rolling peel-outs (the ultimate torture test of your driveline), drag race and auto X.

OEM / Centerforce the release point gradually gets higher and higher up (when releasing the pedal).

You cant go wrong with stage III+, but can go wrong with stage III (not as friendly on the street, or stage II - center not as durable).

Give the folks at spec a call and talk to them about it. They correctly pointed me to the stage III+.

If i remember, both of the guys I talked to there (back in 2006) had first names starting with a 'J' one was nice, one was hillbilly cocky.

 

If you need a SMF and clutch, as it seems from your questions, Spec can set you up. Last year, I installed a new Spec extra-weight billet steel SMF along with their stage 2 clutch kit. The package included the SMF, disc, pressure plate, throwout bearing, pilot bushing, new flywheel bolts and pressure plate bolts, and a cheapie plastic disc alignment tool. The kit arrived with the disc and pressure plate bolted to the flywheel. I marked the flywheel and pressure plate to index them relative to each other, to make sure that when I installed it, I would be matching it all up as-received from Spec.

I did have the new SMF match-balanced to the old DMF before I installed everything, just to make sure I didn't have a vibration problem, but it proved to be unnecessary. The balance was nearly perfect out of the box. I'd still recommend you have yours match-balanced, just to boost your odds that you won't have to do the job twice.

So far, I'm very pleased with the whole package. With the extra-weight SMF, I have no gear rattle at idle, which often results from swapping a light-weight SMF in place of the DMF. The rattle doesn't bother some folks, but I wanted none of it.

I bought the stuff direct from Spec, ordered over the phone. The entire kit cost me just under $800 last year. Prices may have changed since then.

Live well,

SJW

 

Or try Spec's light weight billet STEEL flywheel at about 21 lbs

 

see, i would assume get rid of 10 more pounds.

Hot Rod did an article one time comparing 1/4 times of a drag car w/ a heavy and then a lightweight flywheel.

What they found is that, yes the heavy flywheel did help launch a little harder, but the lightweight flywheel car more than overcame that initial advantage thru less rotating inertia throughout the entire run. The lightweight flywheel car was faster.

I am not sure where so many people equate loud 'rocks-in-can' transmission noise with a lightweight flywheel.

The only extra noise I get is a slight rattle at WOT, or if you are in too-high-of-a-gear for a hill and try to lug it up the hill.

Other than that, I love my lightweight flywheel. BTW, the friction surface is a removable steel disk that bolts to the aluminum surface. The flywheel teeth are also steel.

 

Transmission in neutral, clutch pedal *not* depressed and you get it. This is especially true on cars with larger than stock cams and near stock idle speed. It's quite obvious on mine, even with full length headers, bullet cats, and Corsa exhaust making some noise. Lots of rattle going on. Push in the clutch pedal and it's gone.

 

Thats not a bad price at all. I would be tempted to get all that plus the shifter and beam plates through ZF doc
anybody order through him? I think he can get you clutches and flywheels if i remember correctly?

 

Just make sure he doesn't get you the crappy made in china throwout bearing.

Don't let someone tell you its ok, because its acdelco.

Acdelco contracts it out to somewhere in china now.

It will come in an acdelco box and say 'made in china'.

Carolina clutch were the people that sold me a 'made in china' ac delco throwout bearing w/ my clutch kit back in '06.

 

..Ok, I know I'm digging up an old post...

Its really not that bad on mine, just a light rapping under the conditions you describe.

But how often do you drive like that?

To save fuel, I always shut the motor down. I never idle it.

 

There were a few things I had wrong with my overall combo. The main issue was that my black tag bell housing had a zr1 ball stud which is twice as long as a normal ball stud. The clutch fork because of this was coming in contact with the pressure plate.

The clutch has actually worked out pretty well all things considered. I took it to the track tonight and on my first pass it was slipping bad. But my next three passes it held as far as I could tell. 500+ hp and tq at flywheel. I dunno if it was a fluke or if the clutch just needed to "warm up" or what

But the thing is, the previous clutch in the car worked fine and had a smf also New clutch did not. http://forums.corvetteforum.com/1578342534-post173.html