Chevelle Clutch Fork Geometry

In the process of installing a T56 6 speed in my 68 Chevelle I have run into some Clutch fork geometry issues. As a result I had to go to a taller throwout bearing to provide the proper linkage and fork geometry. Is this normal?

Daryl

Hey Daryl,

I'm assuming you had a stock 4-speed car and are using the mechanical 4-speed linkage and fork? I am also assuming that the location of the clutch fork is now different than where it was with the 4-speed, causing the geometry issue. (On a side note, this is one of the reasons why we like to run hydraulic clutch systems, as they don't require the linkage and have a lot more flexibility in the mounting.)

A taller throwout bearing might be the way to go, provided the travel of the fork is proper and keeps the bearing in the operating range of the clutch. A shim or spacer can do the same thing. I'm hesitant to say it is "normal", but considering the number of variables with every car, we often need to tailor the install to the particular car.

Let me know some more details... engine, is the engine location stock, what crossmember, which bellhousing, etc., and we might be able to provide more insight. Also, did you get this conversion as a kit from someone, and does that company have advice?

History: Originally the Chevelle was a 6 cylinder with a 3 speed. Around 1980 a 350 4 speed was installed. Since than I have had various V8's in front of the Muncie 4 speed. Currently I have a 496 Big Block in the Chevelle. Engine location is stock. Linkage is stock. The Bellhousing was a stock 621 model. About 5 years ago I tried putting in a 11" clutch and took it back because I could not push the pedal to the floor far enough to get a good release. So the 10.5" clutch went back in.

The current Tremec T56 Magnum project comes with a 6023 Quick Time bellhousing. When installing the current RAM 11" Clutch the same problem came up. I purchased a taller throwout bearing (1 7/8" tall compared to the shorter 1 1/4") and my geometry problems were eliminated. All adjustments are within the specs found in the shop manual. I stayed with my mechanical set up because of price and ease of this project. May change at a later dated.

I was just wondering about this since it seems that all of the clutch kits I have seen come with a short release bearing. The difference I observed between the old 10.5" pressure plate and the 11" once bolted down on the flywheel was that the fingers stood taller on the 10.5 than on the 11". This created about a 1/2" difference in height. It is interesting to note that the release bearing that came with the kit is off center. So when I spin the bearing it wobbles a little. I think this is a defect. Glade I am not using it anyway.

Thanks for your insights.

Daryl

Hey Daryl, any updates?

Yes. By putting in a tall Throw Out Bearing my problem was solved. Transmission is running great. I love the double overdrive six speed. Next project will be EFI once I sell the Muncie 4 speed.

Good to hear that solved your issue!