Piston detonation evidence - 1998 Northstar
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Northstar Engines and System Technical Discussion Discussion, Piston detonation evidence - 1998 Northstar in Cadillac Engine Technical Discussion; Okay so I picked up another motor and transmission back in in July for my son for a $142.00 and ...
  1. #1
    daveyhouse is offline Cadillac Owners Fanatic
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    Piston detonation evidence - 1998 Northstar

    Okay so I picked up another motor and transmission back in in July for my son for a $142.00 and they pulled it. I thought that was good deal, since now he has a spare tranny.
    Any been slowly dissembling it since then. It is now all gutted and was cleaning the pistons with extremely hard and heavy carbon buildup on them, when I discovered number 1 piston on right bank looks like it has pits in it.
    Which I am guessing is from detonation.


    My question should the piston be replaced?








    Thanks in advance for any input,
    Dave

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  3. #2
    98eldo32v's Avatar
    98eldo32v is offline Cadillac Owners Connoisseur
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    Re: piston detonation

    In my opinion,

    If you're asking, then it won't be right unless you do.

    Yes, it has some pitting on it from detenation. I'd personally try wet sanding the pit marks down a bit.

    If you replace the piston, you either have to get a stock size piston and make sure the bore is fine for replacement of the piston.

    You have the piston marked from the bore it came from so it should go back nicely into that bore. The pitting doesn't seem that severe to warrant replacing it.

    Just my 2 cents.....

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    Submariner409's Avatar
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    Re: piston detonation

    As above - smooth the pits and use the piston. Clean all the grooves with the proper used ring broken and used as a (careful) scraper.

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    daveyhouse is offline Cadillac Owners Fanatic
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    Re: piston detonation

    Okay wet sanding it is. I found some pits on other pistons as well but not as bad.

    Thank you for your input guys, it is greatly appreciated,

    Dave

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    98eldo32v's Avatar
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    Re: piston detonation

    Good luck with it........

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    daveyhouse is offline Cadillac Owners Fanatic
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    Re: piston detonation

    Thanks,
    I need all the luck I can get.

  8. #7
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    Re: piston detonation



    OK, Sub, you've probably forgotten more than I know about this. That minor pitting doesn't look like anything of any concern to me. What's it gonna hurt if it is not wet sanded? It's gonna be covered with carbon shortly anyway.

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    Submariner409's Avatar
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    Re: piston detonation

    The engine builder in me says "Make it look pretty" even though I would be the only person to know........

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    daveyhouse is offline Cadillac Owners Fanatic
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    Re: piston detonation

    I do plan on wet sanding, BUT do tell, what is it gonna hurt! I am no pro obviously or I would not be asking.

  11. #10
    Submariner409's Avatar
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    Re: piston detonation

    Quote Originally Posted by daveyhouse View Post
    I do plan on wet sanding, BUT do tell, what is it gonna hurt! I am no pro obviously or I would not be asking.
    Leaving the miniscule roughness alone would hurt absolutely nothing. You seemed concerned, so I replied with what I would do.

    ........... and if you DO sand/wet sand it, be very sure to wash the piston thoroughly in gasoline. One granule of grit in one of those piston ring grooves could make a real mess of a cylinder wall.

    When you bang in the pistons, use copious amounts of engine oil on the rings and entire piston. Use the proper tapered ring compressor sleeve.

  12. #11
    daveyhouse is offline Cadillac Owners Fanatic
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    Re: piston detonation

    Ok, so it is cosmetic only? Sounds good I will do it anyway. He spent enough money on this build already. I am sure it will be no buttermore job, but my son is spending all the money he can on this, so I will try to do this right.

    ----------

    I have a ratcheting ring compressor do you not think this would work?

  13. #12
    Submariner409's Avatar
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    Re: piston detonation

    Sure it will work - but the tapered sleeves make the job laughably simple.

  14. #13
    daveyhouse is offline Cadillac Owners Fanatic
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    Re: piston detonation

    Just my luck, nothing is simple, LOL

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    Re: piston detonation

    Ahh, cosmetic only. Now I don't feel so dumb for asking.

  16. #15
    daveyhouse is offline Cadillac Owners Fanatic
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    Re: piston detonation

    Oh yeah I got this, lol

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