I have a 1973 Dodge Van, 360 engine with about 35,000 since rebuild BUT the van was not started for 10 years.
Have now driven about 2500 miles in last 5 years and recently oil pressure went from a typical 45psi to 65psi.
I replaced oil pressure sending unit, PCV breather & Valve and changed oil & Filter. Used a oil service type pressure gauge to confirm pressure is really at 60-65psi.
Now seeing some oil on top of water pump and appears that oil is seeping from the valve cover gaskets.
Do you have any suggestions about what might be causing this?
I’m guessing the same as Tester above. There’s a spring-loaded valve that’s usually part of the oil pump ass’y, or near to it. When the pressure from the pump reaches a certain psi, the spring compresses enough to allow a piston to move so the extra oil goes back into the sump, thereby limiting the max oil pressure. Problems with that spring or the piston likely. On a 1973, if you are willing to take on some risk, I think what I’d do is drain all the oil out and replace it with diesel fuel. Idle the engine for 10-15 minutes with the diesel fuel in the crankcase. Then drain the diesel out & refill with fresh motor oil, new filter. If the piston is sticking, that might free up the piston. Can’t speak to the safety of yourself or the engine if you decide to try that experiment mind you. I’ve seen it done before on a 67 F100, no harm in that case. Another idea would be to run some synthetic oil instead of dino oil, it’s a good cleaner.
Oil pressure specs are 30 to 80 PSI @ 2000 RPM, your oil pressure may be higher than you remember it to be but I suspect the reason is because a high volume oil pump was installed during the rebuild.