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First off, I'm a noob. I bought a LS1 short block and am finally getting around to cleaning it up for assembly. I found a bad piston during the process. Is it ok to just replace the one or should I go with a new set?
Kinda looks like a 5.3 slug. I'd just clean that up and run it. Unless there's a crack I missed
Pull all the rings off. Break a compression ring and wearing gloves use that ring to scrape/dig all the carbon outta the ring grooves. Scotch Brite scuff pad the skirts and tops in a solvent tanks. Wash rinse and re oil the pins Good idea as well to have a local marching shop "lick" the big ends on a rod hone machine. Just a few strokes to hone/clean/cross hatch the bores and correct any size deformation from re torquing. Everyone thinks only aftermarket bolts do this but I've seen even the original GM bolts cause slight variances that should be corrected now
Save the "I've spun a bearing" threads down the road
With the motor already apart why not go ahead and replace the pistons now?
It's the ideal time to upgrade.
My experience with this amounts to back in 2003 getting an LS1 that had been pulled from a wrecked car. We leaked the motor down it failed leak down on #7 cylinder and another cylinder. #7 already had a federal mogul stock replacement piston in the hole. The others were stock. None of them looked bad to the naked eye. However, testing with a special crack checking dye for aluminum show that several of the pistons shouldn't be reused. It was a dye for chemical checking from MagnaFlux if I remember correctly.
I suggest checking the old pistons with the dye before reusing the old pistons.
While best practice would be to replace the stock piston and not reuse, my 72 vette had the original cast pistons checked for tolerance and magnafluxed back in 1982 when the prior owner rebuilt the engine. The pistons checked out good worked fine with no issues for another twenty years or so. If all parts are in tolerance and crack free it will probably be OK.
Last edited by 99 Black Bird T/A; Nov 6, 2017 at 06:48 AM.
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Does 1 bad piston = all new pistons? 
