Just because the bearings have been changed doesn't mean clearances are right.
I'd try running straight 40wt to see if that makes any difference before tearing into it.
"i reject your reality and substitute my own" - adam savage. i suspect my final words maybe "well shit, that didnt work"
instead of perfection some times we just have to accept practicality
Cats Forever
That is one heck of a swing on oil pressure from cold to warm. I don't have a manual for that engine but is it possible someone tried to convert the oil filter from bypass to full flow and mucked it up? My bet is that something is going on with the relief valve somewhere in the system. With no oil pressure you are in danger of spinning a bearing and or flattening the crank. A new oil pump cannot hurt but usually oil pumps last "forever" as they have an abundance of lube. On the 3J is there a relief valve in the oil pump?
Thank you for the responses. All good ideas. Yes it has a major swing in pressure! Like mentioned low oil pressure doesn't bother me but NO oil pressure does. Its so strange like the pump quits pumping oil. Probably explains why the oil doesn't get warm? It has the field add on kit I believe. 2 filters, one stacked on top of the other. When I bypassed the oil cooler all I did was plug the holes in the filter housing and remove the spring and valve. As for the relief valve on the pump I think its just the thumb wheel thing? Maybe I can remover it and build some shims. 3j568 is the number on engine.