Piston marks...help

[dirt rufus]

I found a short block for sale that the guy is asking a great price for the Pistons all look to be new or doesn't have much time on it but a couple of them have scratches in the actual top of the piston trying to get a second opinion of is this motor going to be usable to be ran thank you

[dirt rufus]

[dereksehi]

There has definitely been something that ran through the engine and gouged the pistons, there is a good chance the pistons are junk as usually marks like that can damage the piston enough to pinch the ring lands tight and seize the ring, this can also cause the top of the piston to get squashed out of shape above the ring land and make contact with the cylinder.

[dirt rufus]

It's a 355 short block eagle 4340 crank and h beams with je forged Pistons guy says it ran good just disassembled it ran it all year. he's keeping the heads and going with a bigger cubic inch. He's asking 1200. I'm not a motor builder...walk away or chance it?

[dereksehi]

For that money I would buy it pull the pistons out and have them checked out and replace the ones that need to be.

[billetbirdcage]

Looks like maybe a screw came out of the base plate of the carb, someone dropped something down the carb/intake, or it ingested something at one point.

Can't really see all the pistons close enough to really say, but the pistons could be reusable if none of the dents are too close to the edge and smashed down on the ring groove pinching the ring in the ring groove. If the rings are free when you disassemble, I wouldn't be afraid to just deburr and smooth the dents and run them again (again depending on the actual damage).

That being said, for the cost I doubt you could get hurt too bad buying it but then again you don't really know how well any of the machine work or assembly was done. I would assume the worst and figure you may need to re-machine the block, resize rods, replace pistons/rings/bearings and re-balance and make your decision off those possible added costs to use it. If you can do all that and still be OK cost wise, then if it doesn't need it your ahead.

[dirt rufus]

Waiting for pics of all the Pistons. Ugh decisions decisions

[TBRE]

If the pistons are forged, you can tape the bores up one at a time, and fluff the marks so they won't spread, or crack. If the pistons rock freely in the bore, the ring grooves aren't pinched. It was running fine with the blems, he didn't know till the heads were pulled off, you might run it like it is after you polish the bad spots. And ,no, the pics didn't load, but I've seen screws come out of the butterflies before, looks ugly, but it really doesn't affect much.TB