Pistons Still Good? Pics inside

[mach4g63t]

I got a guy semi-local with a set of std bore Wiseco 9:1 forged pistons. He is saying that he is selling because his block had been bored or honed too many times so the pistons didn't fit correctly when he used them. He is selling them really cheap, but I don't know if they're still any good. The price really worries me as these are 400+ dollar pistons new.

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My buddy who knows a lot about building engines says they might be no good because the skirts are worn out. He's built a 9 second Honda, so I know he's pretty good with motors, but I wanted to double check. Anyone else got any input?

 

[JusMX141]

The skirts definitely show wear; but it looks more like scuffing than scoring.

The only way to tell for sure is to measure the diameter of the skirts of these pistons and compare them to a new stocker's dimensions.

By his cylinders being barrel-shaped, the downforce of the combustion cycle forces the piston to "twist" inside the bore, loading the piston skirts. Years of motocross racing and building bike engines has shown me the consequences....I've seen piston skirts break clear off.

If I were building an engine, I would stay away from these pistons simply because of their history....but if they measure OK and your bores are in good shape top to bottom, then you shouldn't have to worry.

 

[mach4g63t]

Well, I planned on decking the motor and a top to bottom hone just to make sure it's all good. It's a low mileage bottom end but I'm doing it all for longevity sakes and peace of mind since I'm doing a rebuild. Also, how do you measure the pistons? If they're worn, are they more succeptable to breaking off like you said? Also, the other set of pistons I was looking at were Evo Pistons and they had the same 'scuffing' on the sides, but I was told it was from normal wear.

 

[Defiant]

Have a machinist mike them and find out if they're worn out. You can't tell by looking. And you won't be breaking any skirts off in a mildly-abused street engine.