Need a Little help
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Joined: Sep 2012
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Need a Little help
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.
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.
Safety Car
Joined: Aug 2000
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From: St. Joseph MO
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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?
Drifting
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From: Tulsa Ok
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Drifting
Joined: Feb 2006
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From: New Hartford IA
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.
Burning Brakes
Joined: May 2011
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From: Houston Texas
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.
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.
Drifting
Joined: Feb 2006
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From: New Hartford IA
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.
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.
Melting Slicks
Joined: Jul 2004
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From: Northern Ireland
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.
And it's cheap.
Only other option is to reduce lift somehow.
Unless cam timing was badly off and that lead to the contact.
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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.
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.
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.
Drifting
Joined: Feb 2006
Posts: 1,585
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From: New Hartford IA
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?
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?
Last edited by slow ride; Aug 14, 2014 at 07:58 AM.