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Damaged Piston Reuse?

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Old Oct 19, 2017 | 07:18 AM
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Default Damaged Piston Reuse?

Is it safe to use this piston. I sanded the sharp edges and the piston head is smooth, it does still have small indentions due to metal fragments that were in the cylinder. As you can see, the exhaust valve hit, the head is getting fixed as well. I didnt know if it was safe to reuse this piston. I have read a lot about it and everything I read said it will be good to go as long as there are no sharp edges to recreate hot spots. I haven't thoroughly cleaned the piston yet so anything on there is just residue there are no more sharp edges or high spots. Also, I read quite a bit about polishing it and its a 50/50 split, seems leaving them a little stuffed helps with collecting the carbon and better distribution. This is on a stock ls3 engine. No internal mods.
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Old Oct 19, 2017 | 07:33 AM
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why would you want to collect carbon on top of a piston? I'd be more worried about what the cylinder wall looked like.

Last edited by CMY SIX; Oct 19, 2017 at 07:34 AM.
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Old Oct 19, 2017 | 07:36 AM
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Originally Posted by EBuckC6
Is it safe to use this piston. I sanded the sharp edges and the piston head is smooth, it does still have small indentions due to metal fragments that were in the cylinder. As you can see, the exhaust valve hit, the head is getting fixed as well. I didnt know if it was safe to reuse this piston. I have read a lot about it and everything I read said it will be good to go as long as there are no sharp edges to recreate hot spots. I haven't thoroughly cleaned the piston yet so anything on there is just residue there are no more sharp edges or high spots. Also, I read quite a bit about polishing it and its a 50/50 split, seems leaving them a little stuffed helps with collecting the carbon and better distribution. This is on a stock ls3 engine. No internal mods.
that piston is a wall hanger
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Old Oct 19, 2017 | 07:40 AM
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Originally Posted by CMY SIX
why would you want to collect carbon on top of a piston? I'd be more worried about what the cylinder wall looked like.
Cylinder wall has no damage at all.
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Old Oct 19, 2017 | 07:53 AM
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It will probably be ok under normal circumstances. It kinda like a valve relief Racing, I would replace it if possible. You would want a OEM piston, because aftermarket pistons many times have a weight by several grams. With all the buffing you want to be sure to clean up all debris.
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Old Oct 19, 2017 | 08:00 AM
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Originally Posted by Kevova
It will probably be ok under normal circumstances. It kinda like a valve relief Racing, I would replace it if possible. You would want a OEM piston, because aftermarket pistons many times have a weight by several grams. With all the buffing you want to be sure to clean up all debris.
Thanks Kenvova. It is normal conditions, I dont race it and only occasionally run it hard. I have no intentions of doing any internal mods, ie turbo or NO. IF or when i ever replace it, it would be with an OEM piston. Im not getting into the after market pistons.
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Old Oct 19, 2017 | 02:39 PM
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$100 or so for a new piston vs $3k+ for a short block ? Put a new one in and never worry about it.
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Old Oct 19, 2017 | 06:57 PM
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Originally Posted by Patsgarage
$100 or so for a new piston vs $3k+ for a short block ? Put a new one in and never worry about it.
Its not the $100 or so.. its the means of pulling the motor out to replace the piston, unless you know of a way to do it while its still in the car?
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Old Oct 19, 2017 | 07:43 PM
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Originally Posted by EBuckC6
Its not the $100 or so.. its the means of pulling the motor out to replace the piston, unless you know of a way to do it while its still in the car?
I thought the engine was out already, that does complicate matters somewhat. I guess you could pull the other head and get the engine high enough to clear the crank, but at that point it would be less work to pull the engine. Sounds like a good opportunity for some upgrades. I would still be leery of reusing that one, it would always be in the back of my mind.
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Old Oct 19, 2017 | 08:02 PM
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IMHO - I would NOT reuse that piston !!! It's likely that when the piston tried to compress whatever metal was in the combustion chamber - that it cracked the aluminum and did more damage than you can see with your eyes. Sure - it may last years - but it also may fail in 10 minutes. Typically - when they fail - they take other expensive parts with them.

If this was my lawn mower I'd consider giving it a try - but not a Vette motor !!!
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Old Oct 19, 2017 | 08:10 PM
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Originally Posted by Purple92
IMHO - I would NOT reuse that piston !!! It's likely that when the piston tried to compress whatever metal was in the combustion chamber - that it cracked the aluminum and did more damage than you can see with your eyes. Sure - it may last years - but it also may fail in 10 minutes. Typically - when they fail - they take other expensive parts with them.

If this was my lawn mower I'd consider giving it a try - but not a Vette motor !!!
It was the porcelain from the spark plug.
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Old Oct 19, 2017 | 09:23 PM
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I wouldn't...but I'm not really a gambler.
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Old Oct 19, 2017 | 10:31 PM
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My vote: No

What's the saying, "Penny-wise pound foolish?

Your risk...engine still in car I read.
I think you have motor damage and you should pull the engine and make sure you repair it right.
Else, you can go with your repaired piston and hope it doesn't explode further and cost even more time and money....that's the risk.
No one can predict but we do know the value hit the piston top....piston, wrist pin, connecting rod, crank bearings all suffered some indirect damage.
Whether the damage occurred at idle with immediate shut off, or at a higher rpm and continued to run for a minute is not mentioned and I believe make a big difference in the repair plan.

Good luck in your decision.
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Old Oct 20, 2017 | 06:52 AM
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Thanks Kenny. It occurred at idle, never went above 1000 rpms and was for about 30 sec. So does anyone know if I can get to it from the bottom and push it out the top, if I remove the oil pan?
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Old Oct 20, 2017 | 05:26 PM
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Well, the way you normally assemble an engine is to bolt the crank in place, then install each piston and rod one by one. Removal is the exact opposite - so you should be able to unbolt the rod, then remove the rod cap, then push the piston and rod out.

Once the pan is off - I'd rotate the crank till that piston is at BDC, then do the unbolting and removal -- shouldn't be too bad a job - once the pan is off...

As a min - replace the piston. I'd be replacing the rod bearings as well - cheap insurance. If the piston doesn't rotate on the rod super easy - I'd replace the piston pin as well.....
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Old Nov 1, 2017 | 08:16 AM
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Update: I appreciate the feedback from everyone. I was really tempted to change the piston, rod, bearings out, however after speaking to knowledgeable individuals, a few mechanics and performance gurus, I elected to keep the piston and clean it up.So, I did just that, sanded down the piston head, taking off all sharp edges and installing new intake and exhaust valves. Put it all back together and runs like a champ. Moral of all this is do research, read and ask the right people. The piston was fine with no other damage.
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Old Nov 2, 2017 | 04:38 PM
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Is that the same piston? I don't see the valve mark
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Old Nov 2, 2017 | 09:11 PM
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Originally Posted by EBuckC6
...after speaking to knowledgeable individuals...ask the right people...
I'm glad I didn't chime in earlier with all you non-knowledgeable wrong people...
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