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piston failure- need help

Discussion in 'The Hokey Ass Message Board' started by 32/34 Ford, Aug 31, 2011.

  1. 32/34 Ford
    Joined: Sep 28, 2009
    Posts: 7

    32/34 Ford
    Member
    from NY

    Is there any reason other than a defective piston that would cause this failure? The piston is from a 1950 Merc bored . 125 " oversize. It is from a low mileage engine operated at usual highway speeds 2500 t0 2700 rpm.

    Thanks alot for any help you can give me.
     

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  2. JohnEvans
    Joined: Apr 13, 2008
    Posts: 4,883

    JohnEvans
    Member
    from Phoenix AZ

    Without having the poison in my hands to look at the fracture line hard saying ,but defective is as good as any reason. That IS a strange failure indeed.
     
  3. wristpin
    Joined: Aug 31, 2009
    Posts: 48

    wristpin
    Member

    looks to me like you have a rod tweaked to the left/right i would check wristpin bushing/ rod bent for wear like that. look at the top ring land,shinney on one side
    and not the other indicates bent or stress.
     
  4. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    I can't say for sure what happened in your case. I can tell you that it isn't unusual for cracks to start from the slots milled into the bottom of the oil ring. That's why race pistons have holes instead of slots. High RPMs put a lot of stress on pistons and rods. I would have expected that was a factor. It appears you might have an old school sand cast piston. If so, that's another factor. Those aren't the best for durability or performance.
     

  5. wandi harry
    Joined: Jul 19, 2008
    Posts: 261

    wandi harry
    Member

    Nasty, how did the bore end up?
     

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