1969 L71 427/435 Engine Rebuild; Which Pistons, Cam, Etc.. To Use? - NCRS Discussion Boards

1969 L71 427/435 Engine Rebuild; Which Pistons, Cam, Etc.. To Use?

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  • Duke W.
    Beyond Control Poster
    • January 1, 1993
    • 15672

    #16
    Re: 1969 L71 427/435 Engine Rebuild; Which Pistons, Cam, Etc.. To Use?

    Has the engine already been disassembled? If it has, you probably missed the first step in compression ratio management, which is to measure deck clearance of all eight prior to block tear down.

    If the block is bare, a machine shop should be able to measure actual deck height, then you make the final clearance measurements upon assembly and select a suitable head gasket thinckness to achieve the target CR, My recommendation for SHP big blocks is not to exceed 10.3, but get it as closed to this as possible with a maximum variation of 0.1 between the higherst and lowest across all eight cylinders.

    As built, most Corvette engines are up to half a point lower than advertised by GM, and by the time you do a little chamber grinding to even out the combustion chamber volumes, the assembled CR may be another two-tenths lower even with the OE head gasket, and thicker gaskets are readily available.

    Duke

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