Unfortunately yanking the heads would be my next move. Have them pressure checked, resurfaced, valve guides checked/lapped, replace gaskets and hardware, etc. Youre pulling vacuum too much from somewhere in the chambers. Throw some mods in there for sure too. That was my plan, but I had much larger issues.
There is a remote possibility your getting fuel dilution as well and its lowering your oil viscosity enough to flow material through the PCV more than it should. Is your oil pressure staying consistent throughout the full oil change interval? This was something I thought of that possibly contributed to my engine failure. Lifters not pumping up were dumping fuel into the engine on cold starts, and average oil PSI dropped slowly throughout the entire interval. I had TONS of milk in the intake and manifold. When you did the seals did you notice any contaminated oil sitting in the heads? Any oil spotting on the valley cover? Is the back of the throttle body blade caked with oil? Would be a good thing to change that gasket too even though its highly unlikely it would suck out oil or moisture that way. New valve cover gaskets were installed I assume?
I feel ya on the too good to be true truck, man. Sorry to hear it, but seems like its something you can repair.
It’s definitely got me stumped. I think I’m gonna grab an LS6 valley cover and see if that helps. Read a lot of people have my same issue (maybe not quite as bad) and going to that style PCV and plugging the valve cover ones remedied it. I figure, even if it doesn’t help, I’d want to do that anyway when I throw it all back together if I do have to pull there heads.
I don’t believe I’m getting fuel dilution, but I’m only at about 2k miles on this oil change and only had the truck a month. Oil pressure is perfect, about 30-35psi at warm idle and up to 60-65psi under acceleration.
When I did the valve seals, the oil in the heads looked perfect, no milky-ness at all. Same with when I had the intake off, what came out of it was black, no weird colors or anything and smelled fine. I did fresh plugs, new valve cover gaskets. I wonder....I might ought to recheck those, I have no leaks but I wonder if one could’ve rolled in just the right spot to cause a vacuum leak but no oil leak?
I’m gonna do a compression and leak down test this weekend, that should uncover if I have a head problem.
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