External vs internal balance - NCRS Discussion Boards

External vs internal balance

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  • Rex T.
    Very Frequent User
    • December 1, 1984
    • 455

    External vs internal balance

    Why are 454 and larger big blocks externally balanced rather than internally balanced? Also, how difficult is it to balance one internally and what about an internally balanced crank for a 454? Just curious. As always, thank in advance for your help.

    Rex
  • Duke W.
    Beyond Control Poster
    • January 1, 1993
    • 15661

    #2
    Re: External vs internal balance

    The longer stroke requires greater mass at the ends of the crankshaft to balance the first order rocking that's generated by the reciprocating mass.

    Chevrolet deemed there was not enough space inside the crankcase for the added mass, so they chose to add it to the flywheel and damper.

    I believe some aftermaket rotating/reciprocating assemblies may allow for internal balance in OE blocks for 4" and maybe longer strokes. Others may be able to offer some specifics.

    Duke

    Comment

    • Joe L.
      Beyond Control Poster
      • February 1, 1988
      • 43211

      #3
      Re: External vs internal balance

      Originally posted by Rex Turner (8089)
      Why are 454 and larger big blocks externally balanced rather than internally balanced? Also, how difficult is it to balance one internally and what about an internally balanced crank for a 454? Just curious. As always, thank in advance for your help.

      Rex
      Rex-----

      The reasons for external balance are as Duke described.

      It's not too difficult to convert a crankshaft originally designed for external balance (e.g. Chevrolet 454, 400) to internal balance. However, it's expensive. It usually requires that slugs of mallory metal be added to certain crankshaft counterweights. For all practical purposes, I don't see any real reason to do this when one can just go with the external balance and counterweighted flywheels and balancers.
      In Appreciation of John Hinckley

      Comment

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

        #4
        Re: External vs internal balance

        It is possible and not too expensive to do by using mallory metal (which is expensive) I know of at least one Duntov with what was supposed to be a 427 actually had a 454 with internally balanced crank, but the correct flywheel and balance for a 427.
        Dick Whittington

        Comment

        • Rex T.
          Very Frequent User
          • December 1, 1984
          • 455

          #5
          Re: External vs internal balance

          Does anyone know anything about a big block crank called Kryptonite, made by LA Enterprises? Seems I remember hearing of them several years ago as being a premium crank for racing and hi perf applications. Just curous. I wonder if they are internally balanced.

          Comment

          • Clem Z.
            Expired
            • January 1, 2006
            • 9427

            #6
            Re: External vs internal balance

            Originally posted by Rex Turner (8089)
            Does anyone know anything about a big block crank called Kryptonite, made by LA Enterprises? Seems I remember hearing of them several years ago as being a premium crank for racing and hi perf applications. Just curous. I wonder if they are internally balanced.
            just look for circular shaped pieces pressed into the face of the counterweights. some older balance jobs pressed the weights into the edges of the counterweights but this was a bad idea as centrifugal force could throw them out unless they were welded in.

            Comment

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

              #7
              Re: External vs internal balance

              Originally posted by Clem Zahrobsky (45134)
              just look for circular shaped pieces pressed into the face of the counterweights. some older balance jobs pressed the weights into the edges of the counterweights but this was a bad idea as centrifugal force could throw them out unless they were welded in.
              They will make a heck of a hole in the side of the pan if they come out!
              Dick Whittington

              Comment

              • Clem Z.
                Expired
                • January 1, 2006
                • 9427

                #8
                Re: External vs internal balance

                Originally posted by Dick Whittington (8804)
                They will make a heck of a hole in the side of the pan if they come out!
                most balancers would weld a expansion plug in the hole to keep the weight in place since you can not weld tungsten except in a inert atmosphere. i have seen the pressed in ones come out.

                Comment

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