Nasty, remember our conversation regarding chromoly rings & the something about them that is sensitive to overheating? Figured it out a couple of weeks ago while having a very close look @ mine (the LS6 block pulled last Winter). The chromoly coating flaked off in a few small areas. It's enough to create a pressure loss. Have been doing some research & found that a pure plasmamoly coating is less apt to flaking due to overheat & knock, compared to a chromoly coated ring. This means that I don't absolutely have to pay big money for a non-moly coated steel or ductile iron top ring.
Man! Am feeling a lot better now. It's been some time since the first incident, a few years ago, mid-06, when the original LS1 block lost compression after an overheat.
For those reading, an overheat does not necessarily cause the chromoly coating to flake off of the stock piston rings. It's more likely a combination of an overheat in combination with the pre-detonation (knock) associted with it. If it were to happen, the event can be diagnosed with a leak down test. Would expect the chromoly to flake before a head were to warp, for those wondering. Same might be said over a blown head gasket.
Sorry for rambling on, but, not learning the actual cause has been bugging me for years now.
