whiteseven

iTrader: (8)

I have a heads/cam stock bottom end LS1 motor that was run on a mail order tune too long. I took the car up to have a tune done and it was down about 100hp on power. When the engine was scoped by the shop on the #5 and #7 pistons they said the faces look like they've seen detonation but the edges of the piston and cylinder walls look brand new. No compression/leak down tests were done. The plugs showed white peppery residue consistent with detonation.

Which leads me into the following question: if the edges of the piston look fine through the scope, is it most likely the low numbers are a result of the valves being burnt? If I pull the heads and clean off the piston faces and there isn't any pitting/cracks/etc is alright to continue to use the short block and just have the valves replaced in the heads?

The engine isn't burning any oil which leads me to believe that there isn't any significant damage to the pistons, but I don't have a ton of experience diagnosing this problem.

O2Form

Do a leak down test...that will tell you exactly whats going on. Hard to believe the top rings don't have some type of damage if the piston looks damaged. Rod bearings too....

whiteseven

iTrader: (8)

I'm just going based off of what the tuner said he found when they scoped it. I'm going to do the leakdown today.

O2Form

The edges of the pistons might look ok but i;'m talking about the rings themselves. You can't see them with a scope.