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My 454 came with the big flywheel. I am assuming that there is only 1 flywheel size that comes with a big block (with 4 speed). My question is: Is the big flywheel machined for either an 11" or 12" clutch?? I don't remember if it had two sets of holes for 2 different size clutches or not when I dropped it in the engine bay, and I have to wait until I have time to get underneath it to check it out again. I bought a 12" clutch, and I didn't know that there would be problems finding a bellhousing for it.

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Joe

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1965 Chevelle SS
 

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Not for sure on big block stuff, but....
My SB has an aftermarket big flywheel, and it will take both 10.5" and 11" clutch. I think you would have to have a "special" flywheel for a 12" clutch. I don't think cars normally use 12" clutches. I've been reading about trucks using 12" clutches, so maybe you need a 12" 454 truck flywheel. I'm sure somebody knows for sure...........right guys??


chris
 

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AS FAR AS I KNOW, THE BOLT PATTERN ON A BIG, 14in DIAMETER FLYWHEEL, REGARDLESS OF WHETHER IT CAME OFF OF A 350, 427 OR 454, CAR OR TRUCK, WILL ACCEPT EITHER AN 11 OR 12 PRESSURE PLATE. I once had a 12in pressure plate in the shop, but I must have used it for a core trade-in on an 11in pressure plate. Although, I do still have the 12in clutch disc. THE 12in DISC EASILY FITS WITHIN THE BOLT PATTERN FOR AN 11in PRESSURE PLATE. As I recall, the bolt holes on the 12in truck pressure plate were tucked in real tight to the pressure plate. Therefore, as I said, I'm sure both an 11 and 12in pressure plate use the same bolt holes on a big, 14in flywheel. But, for a car application, I just don't think you need the bigger, heavier 12in clutch. That's an awful lot of mass to spin at the rpm of a medium or high perf engine. Truck motors don't spin that fast.
And also, I DO NOT BELIEVE anything bigger than a 14in flywheel can fit within the confines of the truck bell housing. So, if you have the big truck flywheel, use it with an 11in clutch. Remember, a 454 flywheel is EXACTLY the same size as a big flywheel used on a 350-396-427, but the 454 flywheel is all by itself because of the required extra weight on one side for balance purposes (if you are building a SB400 with a 4sp, use a 454 flywheel on the SB400 and just have it balanced with the engine, because flywheels for SB400s with a manual tranny are super scarce).

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Tom Parsons
 
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