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Thread: balance question

  1. #1
    Senior Member RACING JUNKIE
    Join Date
    Sep 2007
    Posts
    4,143

    balance question

    Ok I bought a 454 bone stock to put in my street car.The plan was just to overhaul it stock since this is a car that will not be raced. Well I started the tear down and found the thrust shot on the crank. Someone had replaced the bearing but left the crank.....I can literally pull the crank back and forth an eighth of an inch with all the rods and pistons in it. It is a cast iron crank,so I am not going to fool with having it repaired. Now for my question.

    I have a factory gm steel crank from a 454 I had in my Nova several years ago.I actually have the entire rotating assembly.It has Eagle rods and pistons with a 50cc dome. I had that assembly balanced with a fluidampr balancer that I no longer have. They added some weight to the crank when they balanced it. I don't want to use the high compression pistons. Can I use that crank and those rods with some different pistons and a stock balancer without having the whole thing balanced again? What about using the factory rods and flat top pistons with the steel crank? Since it had weight added to it will that make it way off with the factory rods and pistons? I realize the best thing would be to balance it,but I am trying to do this without spending a bunch of money..BUT if it will cause problems I'll balance it...just don't want to if I don't have to.

    Any opinions

    Thanks

  2. #2
    Senior Member RACING JUNKIE
    Join Date
    Jan 2006
    Location
    La.
    Posts
    2,890
    If the steel crank assy was ext. balanced, Pull the pistons off the rods, find someone with a grams scale and weigh the flat top pistons and the dome pistons. If the flat top pistons are heavier than the dome pistons, you can remove weight by drilling/spot drilling below the pin bosses to make them the same weight as the domed one. You will then have the same balanced rotator. HOWEVER if the flat top pistons are lighter, you have no options except to re-balance the unit unless they are very close in weight.
    There should be no difference in the stock external balancer and the fluid dampner since they are both counter weighted.
    Some would say if it's a 6" balancer VS an 8" balancer, there would be a difference, maybe at 9,000 RPM's but not on the street.
    Just don't forget to use the ext. balance flywheel.

    Zip.


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