Possible cylinder head swap-info needed - NCRS Discussion Boards

Possible cylinder head swap-info needed

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  • Joseph E.
    Very Frequent User
    • February 28, 2006
    • 175

    Possible cylinder head swap-info needed

    One of my cars has a big block engine in it with a pair of 840 cast iron Chevrolet cylinder heads on it. I'm thinking about upgrading the heads to an aluminum set for some weight savings and better thermal efficiency. Induction is via an 8-71 supercharger with two big Holley carbs on it. The car is obviously not stock but she is a blast to drive!
    Compression ratio and piston type is not known but the compression must be fairly low because it is blown and it runs fine on premium pump gas. How would compression and engine performance be affected if I were to go from the closed chamber 840 heads to an aluminum set of Brodix heads with an open/semi open chamber and 115cc chamber volume? What is the approximate chamber volume in cc's of the 840 closed chamber heads? Any opinions and information would be appreciated. Thanks

    Joe 45420
  • Joe L.
    Beyond Control Poster
    • January 31, 1988
    • 43191

    #2
    Re: Possible cylinder head swap-info needed

    Originally posted by Joseph Evans (45420)
    One of my cars has a big block engine in it with a pair of 840 cast iron Chevrolet cylinder heads on it. I'm thinking about upgrading the heads to an aluminum set for some weight savings and better thermal efficiency. Induction is via an 8-71 supercharger with two big Holley carbs on it. The car is obviously not stock but she is a blast to drive!
    Compression ratio and piston type is not known but the compression must be fairly low because it is blown and it runs fine on premium pump gas. How would compression and engine performance be affected if I were to go from the closed chamber 840 heads to an aluminum set of Brodix heads with an open/semi open chamber and 115cc chamber volume? What is the approximate chamber volume in cc's of the 840 closed chamber heads? Any opinions and information would be appreciated. Thanks

    Joe 45420
    Joe------

    The chamber volume for the '840' heads was 107 cc. So, using 115 cc heads will result in a reduction of compression, all other factors being equal.
    In Appreciation of John Hinckley

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