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1970 400 heads on a 1972 455 block

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  • 1970 400 heads on a 1972 455 block

    I had a 455 engine built and they used 400 heads from a 1970 GP with big valves. Now I am told the heads build too much compression. One of my problems is I paid to have the heads ported and that was $600.00 more. Pistons are flat tops and cam is a Comp 268 dur./454 lift. I am looking for help. What can I do. Is my money lost ? Thanks for any help.

  • #2
    Hey Guys, I know some of you has a fix for me. I sure need one !!

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    • #3
      Have I not given what is needed for a reply to my post.
      ???

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      • #4
        it is hard to give a reply you did not say what heads { 48, 16, 12, they are not the same] you did not say if the 455 was stock bore or hog out by .060
        but going on a 455 you will be ok with good gas 93
        1965 GTO 455 JBP 4 speed M-21 12 bolt rear with 3.73
        1969 GTO 400 4 speed air matching # total stock
        1968 Tempest Conv

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        • #5
          13 heads are 72 cc
          ​64 heads are 87cc
          both heads are form 70 GP
          1965 GTO 455 JBP 4 speed M-21 12 bolt rear with 3.73
          1969 GTO 400 4 speed air matching # total stock
          1968 Tempest Conv

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          • #6
            Thanks onebad65, the bore is stock and the heads are either 12's or 13's. with 72 cc. Engine is in storage and not here with me. I had read that these heads would put me in the 11 1/2 to 12 cr. You can read so much and see so many views that I figured I should ask.

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