69 GTO Build

[andrewb70]

Eric,

I can give you my own experience with a light weight clutch and flywheel combination and you can decide how much of it is applicable to your build.

I had a 1988 RX7 with a LS6 engine. The engine was mostly stock with the exception of a fairly mild cam, and made about 400rwhp. The clutch was a Quarter Master single disk 8.5" diameter with a super lightweight billet steel flywheel. The whole assembly came in under 20 pounds:



The transmission was a Liberty modified face-plated (dog ring engagement) T56.

From a drivability standpoint, there were no issues after I learned how to get the car moving. With a "normal" clutch you simple start to release the clutch while at the same time applying throttle. This didn't work very well, as the engine wanted to stall. I suppose I could have fed more throttle, but for some reason I developed a different technique. Just before I started to take off, I would blip the throttle just a little, hitting maybe 2000-2500 RPM. As the engine started to come down, I would start driving in the normal fashion, that is, releasing the clutch and applying throttle. This worked very well and after a while became second nature. The little clutches don't like to be slipped as this generates too much heat, so a quick release of the clutch is beneficial, hence the blipping of the throttle. Once under way, it was just like any other car.



The stock LS tune usually incorporates a slow idle down, which I think was done for emissions reasons, this actually helps with the drivability since the RPM drop between shifts was slow. All in all, there wasn't much downside.

The benefit was that the engine revved up very fast. In fact, it was so fast that I would throw belts as the stock Corvette tensioner couldn't keep up. I solved this by using a Katech non-spring loaded tensioner, which solved the problem. In fact, Katech developed this tensioner just because of this problem on the C5R program.

Another up-side was that the transmission shifted much smoother, and faster than with the stock LS6 clutch. I attribute this to the low overall mass and lower MOI (moment of inertia) of the flywheel/clutch assembly.

Here is an old crappy video of the car at the drag strip:



You can hear how fast the shifts are as it sounds almost like an automatic trans.

All that being said, I think a good compromise might be the new Monster clutch set-up that uses a custom billet (available in 28 or 18 pounds) combined with the new LT1 9.5" diameter dual disk clutch.

http://monsterclutches.com/1998-2002...t-fbody-clutch

I am actually considering this set-up for my Cougar project.

Hope that helps.

Andrew