scratched piston

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Underdog
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scratched piston

Post by Underdog » Sun Sep 30, 2018 11:01 pm

While opening the motor plate with a drill for the head gasket to fit properly,(check picture), I got careless and badly scratched the top of the piston because it was on tdc #-o . My question is, can I run it like that or does it have to be replaced?

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DCal
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Re: scratched piston

Post by DCal » Sun Sep 30, 2018 11:17 pm

It looks superficial to me, I've carb stud imprints and roller needles marks and those pistons were fine.

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Re: scratched piston

Post by rustbucket79 » Sun Sep 30, 2018 11:50 pm

Buff any high spots with a stone or file and run it

lucky
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Re: scratched piston

Post by lucky » Sun Sep 30, 2018 11:51 pm

You may choose to blend the damaged areas with a cartridge roll. Although not likely in the life of this engine, scribe marks have been known to advance into cracks in some instances. A proper blending will most likely eliminate that possibility.
I hope this helps.

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MadBill
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Re: scratched piston

Post by MadBill » Mon Oct 01, 2018 12:03 am

Maybe you could just use the edge of a sharp pen knife blade to scrape off the apparent flakes. That way there's no chance of getting sanding grit down the bores.
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Re: scratched piston

Post by FC-Pilot » Mon Oct 01, 2018 12:18 am

I agree with what has been said. I would try to keep any sanding debris out of the bore if possible. For the head gasket, next time you have an issue just trim that rivet off. It is just there to keep the gaskets together. For some marine applications I actually cut them all off and add a head gasket sealer between the layers, so they are not important to the gaskets performance. Just an FYI.

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Re: scratched piston

Post by Tuner » Mon Oct 01, 2018 12:19 am

MadBill wrote:
Mon Oct 01, 2018 12:03 am
Maybe you could just use the edge of a sharp pen knife blade to scrape off the apparent flakes. That way there's no chance of getting sanding grit down the bores.
This ^^ or use a three-sided scraper like this. I'd use a cutting tool of some sort to avoid crumbs of abrasive getting in the bore or rings and ring lands.

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Re: scratched piston

Post by Old School » Mon Oct 01, 2018 12:54 am

Don't do anything except put the head back on, it will be fine. You will do more damage than good trying to smooth it. Don't you know that rough finishes and dimples are the way to power?

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Re: scratched piston

Post by allencr267 » Mon Oct 01, 2018 3:01 am

I'd be more concerned with that apparent gouge that looks to goes past the water passage bead towards the valley.

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Re: scratched piston

Post by BOOT » Mon Oct 01, 2018 5:32 am

This is what I'd do, put the piston at TDC, cover the shortblock in a trash bag, cut a hole for that area and tape if off good, sand, blow it off, wipe it off n run it.
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Re: scratched piston

Post by gunt » Mon Oct 01, 2018 5:47 am

Definitely polish out all sharp edges smooth it out as good with out taking out materail

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Re: scratched piston

Post by mag2555 » Mon Oct 01, 2018 7:50 am

If you wipe a thick bead of wheel Bearing grease around the top circumference of the pistion and a film of it on the Bore walls you can wipe away any grinding or polishing crap very ease!

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Re: scratched piston

Post by Underdog » Mon Oct 01, 2018 9:13 am

The scratches have no sharp edges but they concern me, yet I have no time nor funds this year to replace the piston, I wish I knew that I could have cut the rivet off.
If I run it like that can it create heat spots that can eventually melt the piston?. For now it will be run on motor but eventually it will be shot with nitrous.

to allencr267 that opening above the water passage is an oil return passage that on this block was totally obstructed (solid shut) and it had to be opened up and there is no connecting "scratch" between the two. Thank you for noticing it.

Thanks to everyone for your help I really appreciate it.

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Re: scratched piston

Post by pamotorman » Mon Oct 01, 2018 11:37 am

cover the piston top with grease and hand sand the area thru the grease. the grease will keep the grit contained

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Re: scratched piston

Post by piston guy » Mon Oct 01, 2018 12:49 pm

Tap any high spots or sharp edges LIGHTLY with a SMALL ball peen hammer to reduce any potential for detonation. Bolt it back together and run it.

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