GM 19328743 LS9 [C6 Vette head]

[tt 383]

A simple Google will give you enough reading to fall asleep too...

[A_VAS]

I've personally taken a set of LS9 heads off a vette, and took them to a cylinder head guy on this board for repair. They were the worst he had seen I think he said, LS7 or 9, all of them.
something like .030" of movement side to side on several of the intake valves. Probably a vid of it somewhere, was a head scratcher. These were in a running engine that did not grenade.
locally owned ZR1 corvette with under 25K miles on it. It did not have the stock cam or valvesprings in it...just to clarify.

I don't think coating has anything to do with it. Poor concentricity of seat to guide axis and forcing the valve stem sideways effectively broaching out the guide material...once you fix that they seem to last

[CGT]

I've personally taken a set of LS9 heads off a vette, and took them to a cylinder head guy on this board for repair. They were the worst he had seen I think he said, LS7 or 9, all of them.
something like .030" of movement side to side on several of the intake valves. Probably a vid of it somewhere, was a head scratcher. These were in a running engine that did not grenade.
locally owned ZR1 corvette with under 25K miles on it. It did not have the stock cam or valvesprings in it...just to clarify.

I don't think coating has anything to do with it. Poor concentricity of seat to guide axis and forcing the valve stem sideways effectively broaching out the guide material...once you fix that they seem to last

The LS7 I was involved with was 25k mileage roughly also. Completely stock. Same thing, guides absolutely trashed. That and a couple other things about LS7's have left me somewhat jaded towards them. .

If it is a concentricity issue, then we fixed it. We bought new castings, new valves, valve jobbed everything and went back together with it. Its been fine, but it's always in the back of your head.

[A_VAS]

yes this LS9 got fixed...new VJ, 8 new intake valves...re-used I think 6 of the 8 exhaust valves.
LS7 heads get the same treatment, although usually the intake valves are salvageable

some additional tidbits on this LS9 engine, when torn down:
rings had several flaking areas of moly removed from the face (rings were just trashed)
pistons had pock marks from spark plug trash
musta had a hard life early on
LS9 uses a forged slug, titanium rod, w/ piston squirters
we tore it down knowing the shortblock was trashed, using oil etc. The head checkup was just a precaution, and glad we did LOL

It's was freshened at +005 new pistons from JE, shortened the factory pins to fit new pistons.
rods fitted with ARP bolts, new bearings, etc. Redone heads
with cam and good PAC springs...running confidently now at 700+ rwhp for about 4 years.