[Formulajones]

With an engine built as snug as yours (.0015" on rods and mains) I wouldn't think your hot idle would drop to 20 psi no matter what pump or oil viscosity you're running. While it may be fine, it sure seems low for an engine with tight bearing clearance.

I've personally never had an engine, Chevy, Ford, or Pontiac, that would idle hot with oil pressure that low accept for one, and it was just plum wore out.

I even have a 327 here that I daily drove in the 80's, a virgin short block that had never been rebuilt with a stock oil pump, and hot idle in that was always 35 psi, and about 45 psi anything above that. The short block had over 100,000 miles on it. Engine smoked and burned oil, but oil pressure was always good.

For a Pontiac reference, my bird has an aftermarket Melling pump (trying to remember which one now) and hot idle is always 40 psi and never changes with 10w-30 or 20w-50. My clearances are .002" on the mains, and .0015" on the rods, and any movement in rpm the oil pressure instantly goes up without any delay. At cruise it's always around 70 psi with either oil in it.

You'll probably hear from others that what you have is fine, and it probably is okay and may run fine for many years. I'm just saying I never see oil pressure do that on a fresh engine build here.

On a side note, usually what I've seen that causes low hot idle oil pressures with very little pressure movement when rpm climbs are worn cam bearings. The hot idle oil pressure being low doesn't worry me so much, it's when it doesn't respond much to RPM when I start to have concern. Oil pressure gauge should respond much like a tachometer when you blip the throttle.