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Discussion Starter #1
I'm assembling my first Big Block and I'm wondering if these pistons are too damaged. I also nicked the cylinder wall a little bit. Do I need a new piston and do I need to take my block back to the machine shop?
 

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More for Less Racer
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I would deburr and smooth that one bad ding on the strut rib on that piston.

The ding in the bore won't matter as long as none of the metal was pushed up higher than the bore finish. blend it by hand with a hone stone or 600+ grit paper to be sure.
 

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Damage

Pistons: How were those marks get there. Apparently they were hit with parts flying around from a blown engine? If the wrist pins shafts are not out of round and the pins fit tight or if they are floaters they move without any drag they are OK. X2 on just make sure to deburr the cylinder nick.
 

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I would want to know what rpm range you are going to use with that engine.
The nick in the cylinder wall doesn't look bad but it is hard to tell in a photo.
The impact divets on the pistons are in the worst place possible if you will be running extended rpm. They will cause stress risers which will accelerate fatigue and failure of the pin bosses. If it is a street engine that rarely sees more than 4500 rpm I wouldn't be too concerned. If this is a performance engine that will see much time above that rpm it could be a catastrophic failure waiting to happen.
So the answer is, "yes you can use them but you shouldn't abuse them."
 

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camarodriver67
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I would take the piston to a machine shop and ask if it can be fixed. The picture of the cylinder is blurry so can't tell. You really need to see a machinist because like has been said either one could form a crack.
 

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Deburr and magnaflux, only way to know for sure.

Look salvageable.
 

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Discussion Starter #7
Thanks for the help everyone. I smoothed the little nicks in the cylinder walls. This will be a street engine that rarely sees over 6,000rpm. I have to take the block back to the machine shop for some rod clearance issues so I'll have them check out the piston while it's there.
 

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Building an engine, especially your first one can be a daunting task, so kudos to you.


It looks like you used a 13 - 15 mm socket on an extension bar to knock the piston out. I have seen that done before, but as you see it damages the piston. Best is a large hard wood dowel (3/4 or 1 inch hardwood) works ok usually. Just hit it as hard as you need to in order to walk it out of the cylinder.


Below is a couple links I found on you tube that shows disassembly of an engine.

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camarodriver67
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I see you read some of the posts by your post #8. But you didn't give an explanation of what happened to the pistons asked by arnoldsel in post #3. Your answer could change the way some people give an answer to your post. Was this a running engine that blew up at high rpm? If it was a person answer might change from just deburr and smooth the bad ding, to take the pistons, rods, and crank to a machine shop to have magnafluxed and checked for cracks and see if the piston has enough material so it can be machined smooth. If I disassembled an engine and saw damage like that I would take the block to see if it will clean up at .060. If it will I would purchase a new set of pistons & rings. https://www.summitracing.com/parts/sum-17350-60/overview/make/chevrolet https://www.summitracing.com/parts/sum-133-139-60/overview/ and rebuild the complete engine checking every part.
 

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Mopar for life!
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Those "ding" marks at the pin bosses have me concerned. Certainly material deformation took place that may cause resistance of a smooth pin rotation.
 
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