502 engine has partially melted piston
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502 engine has partially melted piston

  1. #1
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    Default 502 engine has partially melted piston

    I just rebuilt one of my 502 Mercruiser engines and after 4 hours of use the #4 piston partially melted. Not sure what caused this and welcome suggestions. The builder installed new aluminium pistons and stainless valves. We have sent the injectors away for inspection and they came back good. All the valves and pistons look clean (even the melted one)like there was no detonation issues. Rings in good shape also. Any ideas what caused this??

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  3. #2
    Senior Member wagspe208's Avatar
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    Heat?
    Last edited by wagspe208; 08-28-2017 at 10:47 AM.

  4. #3
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    Lol, Waspe. If it is not pre ignition then it has to be lean on that cylinder for some reason.

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    Senior Member Bubbletop409's Avatar
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    I bought an Edelbrock manifold years ago that had the carb stud holes drilled all the way into the ports. Never noticed the defect during assembly, leaned that port and burned that piston. American made Edelbrock said not their fault, told me to pound sand.
    Larry

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    Senior Member wizbang's Avatar
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    LP-25.com Infomaniac's Avatar
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    You will find the injector for that cylinder not flowing worth a crap.
    If For Some Reason I Do Something Worthy Of Recognition. God Provided The Ability And Deserves The Credit.


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