Finally got around to checking oil pressure. Pretty fantastic really. Starts off at 85 drops down to 38 at hot idle. Doesn't seem to be very erratic, maybe 2 psi as the rough hot idle sets in. Back up to 80 psi at 2000 rpm.
I know this doesn't represent oil pressure every where in the engine. Was planning on checking with plastigauge for bearing clearances on the crank and rods, especially the back two rods. I'd like to do the thrust washer to just to say I tried if it really is looking bad on the main cap bearings.

Still seems like excessively bad mpg at about 11. Going to check spark plugs for cracks and proper resistance. ~10k ohms sound right? Why this would give a bad idle and not poor driving performance I don't know.

I know, and have said before, the cam journals and caps on the right head have some wear marks. Is this the where the main oil pressure loss is coming from? Am I just wasting time with the bottom end? Could the bearings be that bad if the oil pressure is so high. Does this thing need a new / remanufactured head?

 

 

I know this is an old thread but what was the outcome? Had exactly same situation with no codes.