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Thread: Big block chevy machining question

  1. #1

    Big block chevy machining question

    I have a GEN V big block, standard deck. I took .080" off the heads to get the comp ratio where I want it. Now the intake doesn't align up properly (it sits too high). What is the formula for the ratio of head milling to the amount that needs to be taken off the intake? Do just the sides of the intake have to be milled or the ends also? Thanks for any help.

  2. #2
    Senior Member EXPERT BUILDER
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    should just need to take the thickness of the intake gasket off i had the same problem with my sbc but i just had .030 off the heads and the gasket was .060 so my machinist took .060 off

  3. #3
    Senior Member RACING JUNKIE TheYellaBrick's Avatar
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    There is a formula and I don't know what it is, but someone on here does. DON'T DO ANYTHING until you are schooled in it and understand the process.
    You can waste a good manifold real quick.
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    Senior Member EXPERT BUILDER
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    i agree just cause i work for me doesn't mean it always will your machinist should know if he's done it a while and is a reputable machinist

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    The formular for a BBC chevy is for every .010 milled of the deck surface of the head .007 has to be milled of the intake face of the head or face of the intake manifold.

    For a SBC for every .010 milled of the deck surface of the head .0123 has to come off the intake face of the head or the face of the intake manifold.

    If we machine a set of heads we all ways correction cut the intake side of the heads so you can buy any intake out of the box and bolt it on.

    BBC ends of the intake to be milled off per .010 is .0193

    SBC ends of the intake to be milled off per .010 is ..0173

    Also if I know whats being done to the heads I will cut the top of the block so the intake does not have to be cut.
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    Senior Member RACING JUNKIE TheYellaBrick's Avatar
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    Carl,
    That method seems to the way to go. Do you mark/stamp the heads and/or blocks when you do cut them, as folks forget or parts get sold.
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    Quote Originally Posted by DrivingMissDD
    Carl,
    That method seems to the way to go. Do you mark/stamp the heads and/or blocks when you do cut them, as folks forget or parts get sold.
    Its marked on the invoice that the heads have been correction cut as there is a charge for that, On blocks the invoice always states what the finish deck heigt is.

    If a guy goes to the dyno and wants to try differant intakes you should be able to bolt any intake on right out of the box.
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  9. #9
    Senior Member RACING JUNKIE
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    Good post Carl, i knew the formula for sm'blk but not for the b/blk, i appreciate. Unfortutenly most of the shops that mill heads, donot mill the manifold side of the heads, it's almost always a problem.
    Thanks again.

    Zip.


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