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clutch specs/motor swap

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by lasvegas, Aug 17, 2001.

  1. lasvegas

    lasvegas 1/2 ton status

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    New ZZ4 crate engine has a one-piece rear main seal. The engines with this seal have a different flywheel bolt pattern then the old 2 piece seal engines so my old flywheel will not bolt to the new engine. I have a part number for the flywheel I think I need to buy but wondered if anyone else might have done this swap already and had it figured out. I bought a centerforce clutch based on my expectation that I was going to use my old flywheel. I talked to centerforce and they said the pressure plate bolt pattern is the same for 11" and 12" clutch, but then I learned there is no such thing as a 12" clutch according to GM. Does anyone know whether the 11.85" clutch is the same thing and people just round the number up or something. This the largest clutch disc size I can find in the GM performance parts manual. Also, does anyone know where I can find specs on GM part numbers for instance, the thickness of the flywheel if I have the flywheel part number?!?!?!? thanks for any info you might have.
     
  2. 73k20

    73k20 Registered Member

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    I ran into the same problem when I did a motor swap about 6 months ago from an 1986 350 to a 1992 350 on my k20. I had to buy a new flywheel for the newer motor because the 86 flywheel wouldn't bolt up. I thought it was just the cranks with the 1 or 2 piece rear seal that made the difference. But a few days ago I learned that neither the 86 or 92 flywheel fit on my 1985 350 that I just purchased last week. I had to buy yet another flywheel today.
    Good luck...

    Who said size doesn't matter?
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    That clutch size is a royal pain. Whatever Gm calls it, thats what it is : ) Everyone commonly refers to them as 12", but I'm betting that is rounded up. Even the 10" clutch isn't 10", its like 10.4 or something.

    Sorry I can't help on what fits what though...I'd say you need an '88 or so K5 flywheel.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
    No anti-theft measures on your truck? No pity when its stolen
     

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