instead of arguing viscosity, how about looking at something more in the assembly process, this combined w/installed distrubuter height when using an AFTERMARKET intake might be a better place to begin.........if not tear down would tell the story.
An oil pump will pump water or cement, it has no place to go except through the passage( this is assuming the LS7 can be used on this motor in the first place.) May break the pump shaft in the process but a GM lifter not pumping 20/50 through, I would eat a monkeys butt.
Neither one of these may be his problem, just a heads up.
Are you thinking that the pump isn't being driven correctly? If that is the case, why is the pressure gauge reading 60-80PSI?
Now... if it is only reading 80 PSI, then that tells me the oil pressure sender is questionable, and John should get a mechanical gauge on there to be sure the digital is reading right.
I know the LS7 lifters are supposed to fit the SBC block. Whether they are a perfect fit? hm... good question.
