Flywheel interchange

[Richard P.]

Will a 3729004 flywheel ('56-'62 Corvette small block) work on a 1968 big block 396 engine? Thanks

[Ken A.]

Re: Flywheel interchange

Assuuming it's used, then either get a bullet proof bellhousing or an insurance policy for your right foot. 396's can way over torque a used flywheel.

[Tom P.]

Re: Flywheel interchange

Yes and no.
ALLLLLLLLLLLL 55-85 Chevrolet V8 flywheels have the exact same bolt pattern for the crank shaft. Thus, they will all physically interchange.
ALL 55-62 Chevy V8 flywheels were the larger, 168 teeth version. BUT, MOST of them only had a bolt pattern for a 10in clutch (replacement clutches are now 10 1/2in). Only the HD/police/truck flywheels got the bolt pattern for an 11in clutch.
Also, the early 168 teeth flywheels had a groove cut into them so that an 11in clutch could not even be used.
Beginning in 63, the smaller, 153 teeth flywheel was introduced and ALLLLLLLLLLL Corvette engines up through 65 (including the 65 396) only got the smaller flywheel/10 1/2in clutch. Then in 66 they went back to the larger 168 teeth flywheel.
SOOOOOOOOOO, yes, you can physically bolt a 55-62 flywheel onto a 68 BB crankshaft and it will work fine. BUT, if it is one of the flywheels with the groove cut into it (shown below), you are limited to using a 10 1/2in clutch.
I do not have a clue what GM was thinking when they cut this groove into the early pass car flywheels!!!






This is a "regular" 168 teeth flywheel which has a bolt pattern for an 11in clutch. Nortice the bolt holes for attaching an 11in pressure plate are out near the perimeter of the flywheel, as opposed to the position of the bolt holes for a 10in pressure plate above.


Now, one last thing about Chevy flywheels.
As I mentioned, ALL 55-85 flywheels are a direct, bolt-on interchange. BUT, for the SB400 and the 454BB engines, the flywheels were UNbalanced, or external balanced if you prefer. That is, they had an additional weight added on the front side of the flywheel which was needed for balancing the rotating assembly (the harmonic balancers were also UNbalanced).
Here is a comparrison of a neutral balance and an external balance flywheel (used on SB400 and 454 engines). All PRODUCTION external balance flywheels were ONLY the larger 168 teeth version. There were NO PRODUCTION external balance 153 teeth flywheels.
Hope this helps with your question.

[Richard P.]

Re: Flywheel interchange

Thanks guys. Ken, I'm an old man and don't go fast anymore!!