Painrace

Most of you guys know over a year ago I sent my car to Katech for upgrades. I continue to be extremely pleased with everything Katech did! THANKS again Jason! During discusion with Jason about what Katech was going to do I decided to have them install a SPEC 2+ clutch. I talked and read a lot and thought this clutch would fill my needs. After drive the car for 6-8 months the clutch began to make a slight noise when starting out or partially engaged. Jason got in touch with SPEC and their technical person told us the noise was normal for a high clamping clutch when hot. I also felt that it was becoming harder to shift sometimes but was not sure. It was fine when cold but a little harder to shift when hot.

Next came Track Attack! Once again, thanks to Jason and Katech. What a blast and it was including meeting so many Forum members and Katech associates and managers that I will remain friends with for the rest of my life. On the track it became apparent the SPEC clutch was not releasing as it should. Shifts were very difficult. I learned and managed through the weekend. Tommy Marquez had sent his car back to Katech for additional upgrades and they had installed a Centerforce clutch. I was allowed to drive Tommy's car a few times and WOW what a difference. I asked Jason to order me a Centerforce clutch. Jason asked if I wanted an aluminum flywheel as he has and I agreed. The clutch came and the installation was completed yesterday. During the installation we could feel the disk hitting what we thought was the pilot bearing. We called Centerforce's tech line and got a guy that could not have been more helpful. He held the line while we knocked the pilot bearing back 1.5 mm as he recommended. After that, everything was easy. This tech guy was one of the best we have ever talked with. A real first class guy that was very interested in helping us and he knew his stuff!

Now, the clutch! WOW, What a difference! Extremely easy to operate and very, very smooth. I cannot believe how easy the transmission shifts. Katech recommended having RPM balance, cryo treat and polish the rear end and transmission which I did and again THANK YOU JASON!. The clutch peddle has about 3/8"-1/2" free play and then another 1' or so and it is disengaged. I have not run the car hard because Centerforce recommends easy street driving for 450-500 miles (400 miles to go ). In addition, I can tell the engine will rev faster. When I let off the gas while slowing down the car coasts much better. I know what a aluminum flywheel will do to breaking distances! I can't wait to try this thing out once broken in. Finally, gas milage is improving!

Many thanks to Jason at Katech for recommending and getting the Certerforce clutch for me. Additional thanks to Centerforce for a fantastic clutch design and function! Say, do you guys know about the patented weights on the Centerforce pressure plate springs that increases clamping force as the RPM go up? It is one hell of and idea. I will let you know how it works. Also a special thanks to Jeff Johnson, my super mechanic! I think this is the clutch Pratt and Miller are putting in the C6RS! What I have is a Centerforce DFX pressure plate and disk and a Centerforce 900 aluminum flywheel (reduced rotating weight by 12.5#!). If you are thinking about a clutch change I highly recommend the above Centerforce assembly. I think you will be as pleased as I am.

Jim

JDRacing

Good write up and thank you for the information. I find it interesting that reduced surging is attributed to a lighter flywheel, as I would think reduced flywheel effect would make the car more prone to surging.

Anyway, glad you're happy with it.

jogar80

VRZ06

Nice write up, let us know what you think in a couple thousand miles. I don't believe you can go wrong with Katech, their a top notch organization

Lawdogg

You are not the first to have that problem with a Spec clutch. Think about the headache for the installer considering the amount of work to change it out to something else.

Fast06Z06

On my old cars with CenterForce clutches we used to have the problem when at the track when trying to get the rpms high the car would actually start to roll forward due to the centrifugal weights with the clutch completely compressed foot off the brake. that was the only down side. Other than that it was all pluses. Sounds like it works well for you. Good luck with it!

stano

Great write-up Jim! I think that's the clutch I'll get when the time comes Tommy is real happy with his as well

Yaroslav

Jim how long does it take to change the clutch?
And if you know: Where can i find an instruction of installation?
Sounds like its what we need for high hp cars!
Thanks

Wulverine

I have run both the CF DFX and LMC disk in my 03 cobra. No complaints at all (LMC more street friendly than DFX). CF will be my choice when the time comes for a new clutch in my Z. Still can believe it didn't come stock with a twin disk setup. GT500's come stock with a twin disk rated at 900 ft lb's torque and is butter smooth.

urslooow

Who reccomended the spec-2 in the first place? had u spoken to anyone who had put a spec-2 in a z prior deciding on it? Must be hard to get that info in any case

Painrace

The clutch and flywheel comes with installation instructions. You can go to the Centerforce site and get some info. You can call them if you have a question. They, like Katech, are first class! My clutch and disk was a DF395010 and the aluminum flywheel was a ctf900142. I think those might be exact serial numbers. The DF and 900 is what is important. I am sure a supplier can help you. Katech (Jason) did it all for me. Good luck.

Jim

Painrace

I got a lot of inputs. A lot of guys love SPEC clutches. I have never had a street clutch feel as good as the Centerforce or work this well, so far. If Katech and Pratt and Miller are using Centerforce now that is a good indication they are good! My experience was "OK" at best with the stock clutch and the SPEC did hold the HP. Just my 2 cents. I am very happy now. You live and learn.

Jim

Painrace

I would check with Jason or Centerforce, Stan, when you are ready. They may have something better. I think Centerforce is also looking at doing a slave and bearing kit. If I had that option I would have also taken it rather than putting a new stock one in.

Jim

Everett Ogilvie

Nice write-up, and your set up sounds great Jim. You mentioned that your new flywheel is 12.5 lbs lighter? What does the stock flywheel weigh? Thanks, and enjoy!

Frenchican

Hey Jim,
Glad to see you are as happy as I am with the Centerforce. Guess those Pratt & Miller guys picked the right clutch for the C6RS.

Been pretty busy lately. Was in Texas last week and just made it home for a 4 hour nap and then headed to Reno for the All Corvette Gathering.

On the way up, I ran Sherman Grade which is along Tioga Pass, Eastern Sierra Nevada mountains at the legal speed limit ofcourse

For those who don't know that mountain, it's rough on the drivetrain. Steep sweepers and hard shifting. My Centerforce and RPM tranny/rear was amazing. Absolutely no drama. Easy transition and snappy speed shifting.

I let a buddy of mine, bpappy, drive my Z for about 30 miles on a poker run. The first thing he said was. "Nice clutch"

Oh yeah, one small item. My Katech Z won 1st place in the show and shine for Best Modified/Custom
Also won Best Engine.
Oh yeah, one more... Best in Show.

stano

Hey, that's cool Tommy! Congrats Buddy!!

Oh by the way, don't let a little fender bender stop you from handing me the keys one day huh

805Z06

Congrats.....


Just a questions...is there any slight chatter which is common on after-market clutches?

Thanks

Jim Shearer

How much stiffer is the clutch pedal? I know a guy that had the same clutch installed on a C6 and he said the clutch felt "heavier". I guess he was referring to the resistance but I'm not sure.

Painrace

My stock one weighed 25#. Both clutch and disks weigh 29#.

Jim

Painrace

None so far but I only have 100 miles on it.

Jim