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compression question

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  • Roger G.
    Expired
    • October 11, 2012
    • 268

    compression question

    assuming a stock rebuild, with 30 overbore, does the piston dome need to decrease to maintain the stock CR?
  • Joe L.
    Beyond Control Poster
    • February 1, 1988
    • 43211

    #2
    Re: compression question

    Originally posted by roger gleason (55547)
    assuming a stock rebuild, with 30 overbore, does the piston dome need to decrease to maintain the stock CR?

    Roger-----


    Everything but the bore size being the same as stock, yes. However, keep in mind that depending on the piston, it may not be possible or advisable to remove enough material to compensate for the compression increase due to the increased bore size.
    In Appreciation of John Hinckley

    Comment

    • Dick W.
      Former NCRS Director Region IV
      • June 30, 1985
      • 10483

      #3
      Re: compression question

      Also be advised that the advertised compression ratio was somewhat optimistic at times. Higher numbers made better marketing. Unless your heads have been cut, I doubt that .030 overbore would get you past advertised compression ratio. The only real accurate way is to CC the heads and block.
      Dick Whittington

      Comment

      • Roger G.
        Expired
        • October 11, 2012
        • 268

        #4
        Re: compression question

        Thanks Joe and Dick

        Comment

        • Joe R.
          Extremely Frequent Poster
          • May 31, 2006
          • 1822

          #5
          Re: compression question

          Roger,

          As a somewhat new member, you may not have seen the compression ratio article that was in the Restorer a while back. It is reprinted in the following newsletter, starting on page 5:



          Joe

          Comment

          • William C.
            NCRS Past President
            • May 31, 1975
            • 6037

            #6
            Re: compression question

            Remember that a .030 overbore is relatively miniscule, and factors such as have the rods been rebuilt (will shorten the rods) is the head gasket thicker than OEM (many high-quality versions are) Have the valves been ground (drops the valves and /or seat and increases chamber volume) generally make a .030 overbore a "no pain" issue from a C/R standpoint.
            Bill Clupper #618

            Comment

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