Silver02Z28

iTrader: (2)

I pulled my driver's side head off tonight, and noticed some scratches on the #7 wall. The scratches run the entire stroke and are deep enough to catch a fingernail on. They are only on one side of the cylinder, and there are three or four scratches that run up and down.

This engine used to be boosted. After my turbo died, I removed it and now I plan to go nitrous. I noticed that the N/A power is way off from before the turbo. I'm now running a mid 13 compared to a 12.8 pre-boost. I was running 5 or 6 psi. while boosted. I wonder if I damaged the #7 piston.

I don't notice any oil burning. I knew I should've done a leakdown before pulling the head! What else could cause scratches like that?

Grimes

iTrader: (3)

I'd make sure that your pistons and rings don't have any damage to them. #7 cylinder tends to run leaner on our cars, so that may be the reason for the malfunction. What are your plans now?

Silver02Z28

iTrader: (2)

I'm pulling the other head for a look. I may be pulling the motor and checking #7 piston. I suspect some ring land damage. The power is way down and I thought it was just bent pushrods but they are all straight. If a hone doesn't clear it up, I'll get it bored and run forged. What's a good set of forged pistons cost these days?

I'm planning on spraying a 100 dry shot. Maybe more if I go forged. I'd like to go back to FI down the road.

Camaro99SS

iTrader: (4)

You have the same problem that alot of 03/04 Cobra guys have, except they have it worse because of the tight factory piston to wall clearance specs. With all that heat, the piston expanded enough to where the rings started scoring the walls and gradually wore into them. Since you're going forged, have the machine shop hone the walls so the piston fits on the "loose" end of the specified tolerances. It may give some cold start piston slap, but it'll save the walls when running 10+psi of boost through. Also, it wouldn't be a bad idea to upgrade radiators if you haven't done so yet.

Jason

Silver02Z28

iTrader: (2)

Thank you for the info guys. I'll be finding out for sure this week. I'll post pics if there is any carnage in there.

EPP

iTrader: (22)

I'll bet you have a broken ringland on the #7 piston. It happens all the time. Bob

Silver02Z28

iTrader: (2)

I'm betting you are right. I just hope I can get by without a bore, but I can catch a fingernail on the scores so I think a bore is in order. Best time to go forged I guess. Maybe a cam while I'm at it.

Camaro99SS

iTrader: (4)

Sounds like you'll have to bore it then. Whatever you do this time, get good rings and a good forged piston, Diamond, JE, Wiseco, etc all make great slugs. Since you're going FI, I don't think I'd worry too much about a "light" version of a forged piston. You'll need to handle boost instead of high rpms.

Jason

Silver02Z28

iTrader: (2)

Pistons are OK. Must have blown some crap through the turbo. New rings and a hone should do it. What are the best rings to buy?

Brandon Boomhauer

iTrader: (10)

Hrmm, but wouldn't you be able to see it? Or could it break and you not see it?

I'm dealing with the exact problems with Pwebbz28's car right now, its down on power bad, has some ticking, and everything "looks good"

PREDATOR-Z

Tight piston to wall clearance??? on an LS1, you must be kidding right?

Ever heard of piston slap?

That is prolly ringland damage or a ring that came unseated or both..

PREDATOR-Z

Not necessarily. It could be below the crown, once you take the piston out, it all comes appart.

Silver02Z28

iTrader: (2)

I took the piston out and found no damage at all. But there was some crap in the oil pickup. Somehow I sucked in some junk.