New jeep to me. 1952 cJ3A. Engine sounds good (no knocking, banging, ticking), valves adjusted, head torqued, compression test variation is between 105 psi and 125psi. The engine is a little smokey when under way, not bad but it's there. I'm guessing rings at this point. But my big concern is lost of oil pressure. At start up the pressure at idle is around 50 psi, under way it slowly drops, 10 - 15 minutes, 30psi -40psi. At idle, 10psi or less, assuming the gauge is near correct.
How do you tell if the oil pressure loss is due to worn engine parts or a worn out oil pump? If the pump is defective do you rebuild it, or, I've read there are quality problems with the new replacements pumps. What to do?
The Willys "Manual" will tell you 10 psi at idle is ok, 30 psi running down the road is fine, IMO your fine. What oil weight are you running ?.. many things can effect oil pressure, bearing condition would be #1, cam bores, lifters beyond that. Your compression is fine, not saying your oil rings are up to spec, I'd run it for awhile and see how it acts before condemning it!..
From what you've described, I would agree that rings are probably your smoke culprit. Your oil pressures seem typical so I don't see any concern here for your oil pump. Tell us about your oil please. Is it synthetic or petroleum? Remember, these old engines were designed to run on single weight oils made from petroleum. If you run synthetic oil then you may clean up the inside too much, thus reducing oil pressure. Not to mention that synthetic can flow more easily than petro oils. And petro multi grade oils usually are a bit thinner than single weight oils.