Pump is out. My o-ring was the correct cross sectional diameter( not the blue one for f & y bodies). And, I was right it was green, not red. kind of a medium green in color. new o-ring, purchased at Sinclair Buick/GMC is also green. A dark, grass like color. I used part # 12563963 to get the ring. The man behind the counter informed me that there was a new part # for this item. The new number is 12584922.
My guess is the o-ring has been changed, or improved. Otherwise, why the number change ???

 

New ring, same ol' pressure. 22-23 idle, 35@2500, 40@3500. Lot a work for no result. When the old 6.0 was pulled, stock oil sending unit was broken. Replaced through the local parts house. I think a test with a mechanical guage is in order, and/or a new sender from the dealer. Any thoughts folks ??
Anyone got the GM number for the sender ??

 

Need to know some specs on the bearing clearances. Some engine are built with looser tolerances which would result in lower oil pressure.
I also believe, not 100 percrnet sure on this, that a ported oil pump will flow more, but show lower oil pressure as well. I would keep an eye on it, see if it is consistant. You still have good pressure. Rule of thumb is 10 psi for every 1000 rpm.

 

I think watching the f'er close, and a check with a mech. guage will be on order for now.