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Thread: Stroking BBC

  1. #1
    Senior Member MASTER BUILDER
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    Stroking BBC

    How big can a bbc be stroked before the block has to be machined. The block is stock gm. Thanks.

  2. #2
    Senior Member MASTER BUILDER
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    Dec 2004
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    out of my mind in Kalamazoo, MI
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    Re: Stroking BBC

    Quote Originally Posted by jreiley
    How big can a bbc be stroked before the block has to be machined. The block is stock gm. Thanks.

    I saw this out there and I tought I would try to answer this....the short deck or tall deck depends on the crank and rods you are going to use usually if going to a 4.125 throw crank you will need to clearance the rods on the oil pan rail...now I'm not sure about the tall deck but be aware that at some point you will need to clearance the crank and rod throws depending on how big you are going....I think the new casting for the big inch crate motors that GM is offering already has those considerations in mind hence the big cubic inch numbers...maybe somebody else has an idea

  3. #3
    Senior Member RACING JUNKIE
    Join Date
    May 2006
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    2,044
    I used a stock 454 block and put 4.25 eagle rotating assembly in and everything cleared, even a stock oil pan without notched rails cleared.
    Maybe I got lucky who knows but I do know the later 454 blocks i've seen do have a little relief cast into the pan rails which looks like it was meant to accomodate a longer stroke. JMO> Cp
    ***IN GOD WE TRUST***

  4. #4
    Senior Member RACING JUNKIE
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    4,143
    I got a 512 casting block that had a 4 1/4 stroke crank in it when I got it...I don't remember seeing any evidence of being clearanced but I wasn't looking for that either.

  5. #5
    Senior Member MASTER BUILDER
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    Re: Stroking BBC

    Quote Originally Posted by radicalz
    Quote Originally Posted by jreiley
    How big can a bbc be stroked before the block has to be machined. The block is stock gm. Thanks.

    I saw this out there and I tought I would try to answer this....the short deck or tall deck depends on the crank and rods you are going to use usually if going to a 4.125 throw crank you will need to clearance the rods on the oil pan rail...now I'm not sure about the tall deck but be aware that at some point you will need to clearance the crank and rod throws depending on how big you are going....I think the new casting for the big inch crate motors that GM is offering already has those considerations in mind hence the big cubic inch numbers...maybe somebody else has an idea
    Thanks for the reply. My thoughts are that I have to replace the rotating assembly anyway and I might as well stroke it. I have very limited access to any good machine shops.

  6. Racing Junk


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