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Thread: Head Gasket thickness selection

  1. #1
    Grumpy Old Man
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    Default Head Gasket thickness selection

    Seen this question asked on many occasions, here's the HG's for dummies version

    1) Stock HG = 1.37mm compressed

    2) Stock head = 116mm deck to valve cover surface

    3) Stock block = 198.5mm from deck to main bearing saddle

    If 2 and 3 are less that amount needs to be added to 1 to retain the stock compression ratio and squish/quench.

    When resurfacing the Block be sure to take the Timing Case along to have it done at the same time or your new HG will fail in miles.


    Block measurement = 198.5mm/7.81"

  2. #2
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    Default Re: Head Gasket thickness selection

    i already have my 1.2mm MHG from HKS
    would it be ok to use since the head is resurfaced?
    if not what would happen?

  3. #3
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    Default Re: Head Gasket thickness selection

    Quote Originally Posted by kamikazemkiii View Post
    i already have my 1.2mm MHG from HKS
    would it be ok to use since the head is resurfaced?
    if not what would happen?
    If the stock gasket is 1.37mm, then the HKS is already to thin for stock surfaces. Since you have already machined the head, (and hopefully the block as well), You will need to get a much thicker gasket to maintain the correct compression ratio, or you will get detonation issues. And if you haven't done the block, then don't even think about using a metal gasket, because it will not seal.
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    Default Re: Head Gasket thickness selection

    Quote Originally Posted by rayall01 View Post
    If the stock gasket is 1.37mm, then the HKS is already to thin for stock surfaces. Since you have already machined the head, (and hopefully the block as well), You will need to get a much thicker gasket to maintain the correct compression ratio, or you will get detonation issues. And if you haven't done the block, then don't even think about using a metal gasket, because it will not seal.
    i havent decked the block just resurfaced the head
    my wiseco's are 9.1 compression
    what size would you reccomend?

  5. #5
    Grumpy Old Man
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    Default Re: Head Gasket thickness selection

    Measure the Head and Block.

  6. #6

    Default Re: Head Gasket thickness selection

    How much is considered safe to remove off the head/block before either is considered junk? I see this question often and it always seems to be unanswered. Also, why did HKS make a 1.2mm head gasket/ in what case should it be used?

  7. #7
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    Default Re: Head Gasket thickness selection

    thats helpful thanks for the info and sticky
    89 turbo about to be put in beast mode

  8. #8
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    Default Re: Head Gasket thickness selection

    Quote Originally Posted by IJ. View Post
    Measure the Head and Block.
    Sometimes the answer is right in front of you, but you just can't see it...........

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  9. #9
    Grumpy Old Man
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    Default Re: Head Gasket thickness selection

    Quote Originally Posted by CyFi6 View Post
    How much is considered safe to remove off the head/block before either is considered junk? I see this question often and it always seems to be unanswered. Also, why did HKS make a 1.2mm head gasket/ in what case should it be used?
    Going by the factory specs very little but in the real world 20 thou off either seems to work fine and possibly more off a late Heavy/Thick Block.

  10. #10
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    Default Re: Head Gasket thickness selection

    Yeah i'd love to know when a head is considered unusable.. I have 3 of them that have come off of BHG cars, and they've all been resurfaced before. I'd much rather not use one that's gonna cause me MORE headaches lol..

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