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Chief Cylinder head quesiton

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  • Chief Cylinder head quesiton

    Evaluating heads, what should the depth of the combustion chamber be for standard 74 heads?

    Is there any other way to tell if they have been faced down too much?

    Also, how tall should the bolt hole bosses be? Can these be faced down too much also and cause bottoming out of headbolts?

    Another question, how close in depth does the head set need to be if you have mismatched heads?

    I supposed some of this could be gained by having the motor together and measuring valve height, but my unit couldn't be any further apart at this time. I have also heard of measuring the volume of the chamber with water.
    _____________________________________________
    D.J. Knott
    AMCA #10930

  • #2
    Too much compression

    Originally posted by Knotthed View Post
    Evaluating heads, what should the depth of the combustion chamber be for standard 74 heads?

    Is there any other way to tell if they have been faced down too much?

    Also, how tall should the bolt hole bosses be? Can these be faced down too much also and cause bottoming out of headbolts?

    Another question, how close in depth does the head set need to be if you have mismatched heads?

    I supposed some of this could be gained by having the motor together and measuring valve height, but my unit couldn't be any further apart at this time. I have also heard of measuring the volume of the chamber with water.
    The machinist milled down my Bonneville heads (took the lip right off. The bike was nearly impossible to start, and overheated immediatly. New heads solved the problem and had a 80 thousands lip.

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