Checkers02

So I have a 2002 Z06 twin turbo that is currently getting head studs thanks to a cheap boost controller. My real worries started after I pulled the heads. With a stock bottom end ls6 and a big unknown cam should there be small crescent moon dents on top of each piston? Or are my valves hitting?
If anyone has pics they could post of stock Pistons I would be grateful. Oh and I sent my heads off but all the valves are fine but some of the valve guides need redone. If that helps any.

JT FRC 00

Valve reliefs in the piston, made that way on purpose on aftermarket pistons for clearance. Guessing you bought this Vette used with the mods already done?

Checkers02

I bought it with the cam but not turbos. I know they put valve reliefs on aftermarket Pistons but these look stock. And the mark on them is about the thickness of a small screwdriver.

stevieturbo

post a photo

Checkers02

All I have is my phone. Just learned my heads have larger valves in them so I feel they kissed the Pistons. Would send someone an email if they wanna post the pic.

JoeyG

Previous owner could have possible done piston relief cuts to clear the cam/larger valves. Best to post a picture. How deep are the marks on the piston tops?

danieloneil01

danieloneil01@yahoo.com


I can upload them for you and post them up

Checkers02

Sent pics thank you very much. If they are relief cuts I sure would feel better!

danieloneil01

danieloneil01

That's what they call "kissing the piston".

Checkers02

Afraid of that. So a thicker head gasket wouldn't be a bad idea I'm guessing.

danieloneil01

I run LS9 cosmetic head gaskets. I would consult an expert though. Maybe you could throw in LS9 gaskets and use a pushrod length checker to find out what length you need.

Checkers02

Awe didn't even think about push rods

slow ride

It looks light, but you never know how bad the valves are from contact. I would have the heads checked and fixed if needed. Flycut the pistons to give more room and make sure the springs/pushrods are up to snuff for control the cam with boost. Don't try to do it with a thicker gasket.

JDS99

Absolutely valve contact. If they were flycut they would have carbon buildup like the rest of the piston surfaces.

Need to account for more than just cold clearance. Lifters can and do start pumping up at high rpm, valves get hot and lengthen, etc.

Personally, I don't like seeing flycut pistons for F/I. There is a huge difference between flycut stock pistons, and aftermarket pistons with valve reliefs.

If it were me, I would change cams and get the clearance needed instead of flycutting.

slow ride

What the heck, it's a stock longblock, hit those spots with a angle grinder with a cutting wheel and let it eat I'm kidding for the most part (it probably would work though haha). Hard to say you might have had enough clearance, but floated the vlaves and made contact. Need to blueprint the valvetrain and KNOW exactly what you got cooking.

stevieturbo

You may be kidding...but it would work for the clearance needed, and it's quite clear where needs clearanced.

And it's cheap.

Only other option is to reduce lift somehow.

Unless cam timing was badly off and that lead to the contact.

Checkers02

That's pretty much how I've felt. It has an extremely aggressive cam in it, and as it sounds mean I know it's a poor choice for turbos. Only problem is I don't really have the cash for another cam and seals yet.
I sent the heads off last week and he called me yesterday. All Springs and valves checked out. Dual Springs and larger valves. 2.050 intake 1.570 exhaust. So combo of everything caused it I guess.

slow ride

I'm with you brother. I'd use a angle air die grinder with a small cutting wheel or course sanding disk and tape up the the deck Building these things isn't rocket science and unless it's a high end piece I do whats cost effective.

From the sounds of the cam a smaller grind would work well here. What is the turbo setup?

Checkers02

Maybe I neled to find a 5.3 ha ha. The turbos are a UPP setup. So twin 58's if I remember correctly.