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Discussion Starter #1
I decided to tear the 393 down the rest of the way last night so I could send the crank over with the new pistons and have it all balanced. This is what I found once I pulled the pistons out.

I believe it wasa either 4 or 5 of the pistons actually look like this. I can see slight scoring in the cyliinder walls also.

I'm hoping that a light hone will take the scoring out of the block, but the way my luck goes it probably wont.


What do you guys think caused this? I would like tofind that out before I go any further.
 

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:eek: I think thats a "OH SH!T" signal for sure!!!
 

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Might have been...
1: It was run for a little while with no air filter and sucked up dust or sand?
2: After heads or intake ported (or even removed/changed), something was not properly cleaned before engine was started?
3: Metal shavings in oil? (not quite as likely as 1&2)

Are the rings damaged?
 

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Discussion Starter #5
Rings are fine.
I think we have it narrowed down to over heating. It got very hot the last time I had it out. It looks like the pistons actually welded themselves to the cylinder walls, this is why it looks like it's torn apart like it is on the top.:eek:
 

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Honing.....

If the cylinder bores weren't honed to what the manufacturer of the pistons say, then that could have caused the piston to try and start to seize in the bore(s).

A friend of mine had the same exact thing happen to his motor and when he took it to another reputable engine builder, they told him it was not honed far enough. After they re-honed the bores to the right specs, he added new pistons and never had a problem again.

Good luck with it, Brent.
 
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