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what causes a hole in a piston

Discussion in '40- & 55-Series Tech' started by pvaman, Sep 21, 2003.

  1. pvaman

    pvaman

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    85FJ60 - 200K miles. Pulled the head and one of the pistons has a fairly good sized (1/2 sq cm) hole in it. What can cause this...a vacuum leak? ???
     
  2. Degnol

    Degnol

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    Pre ignition, timing too far advanced, will burn a hole in a piston. Vacuum leak isn't a big problem unless you're trying to get a smooth idle. A big vacuum leak would make it run lean and hot, but I don't know if it would burn a hole in a piston.
    Ed Long
     
  3. Gumby

    Gumby Supamod Staff Member s-Moderator

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    A vacuum leak can cause pre-ignition.
     
  4. woody

    woody unhelpful spotter Staff Member Admin

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    #5 or #6 piston? IIRC, a bad vacuum booster can cause enuf of a vacuum leak to trash a piston...
     
  5. pvaman

    pvaman

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  6. CruisinGA

    CruisinGA

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    Normally bad boosters are pretty obvious though. Hissing like a pissed snake. How are your brakes pvaman?
     
  7. hammerhead

    hammerhead

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    Do any other pistons show signs of pitting?
     
  8. dd113

    dd113

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    I would bet it was a bad booster or even a good booster drawing on the back 2 cylinders. I have no idea why this happens. It might be that the vac for the booster causes it to run lean but I cant see why this would hole the piston. Could also be a small part of a plug that got in there.
     
  9. bobrose

    bobrose

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    Don't remember off the top of my head what symptom points to what but the type of hole it is can be telling. A hole that looks like it was punched out (fractured edges) vs. a hole that looks like someone took an acytelene torch to it.
     
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