In Reply to: oil pump posted by AAm on October 13, 2017 at 21:37:41:
First things first. Did the pressure drop quickly? Slow decline? drop as you increase the power setting? Good pressure cold and very low at operating temperature.
Check the oil pressure with a known to be accurate mechanical gauge."I know my gauge head and line and are good" isn't a correct answer. CHeck it cold and hot. Pull the oil pressure relief valve. Make sure the valve is free and the spring is in spec.
Shimming the pressure relief valve is not the answer to correct a low oil pressure problem.
Most oil pump problems aren't. You could take an oil sample, spend $17,for an oil analysis (CAT or some NAPAS). When it comes back full of cadmium, copper, tin etc. you will know for sure or you can pull the pan and check the rod and main bearings. Scuffed with a little copper showing on the top shell, bearings are worn, replace them. Copper all the way around. No doubt.
You are going to get answers like "OMG It needs an out of frame overhaul"
If it is running well, has reasonable compression, doesn't use an excessive amount of oil, doesn't smoke and generally behaves except for low oil pressure, rod and main bearings will probably solve your problem. THere are specs in the manual defining the running clearances of the oil pump. Obviously check them. Repair/replace any parts necessary to bring it into spec.
Either way the pan has to come off, a real treat.
It probably just needs rods and mains. If so replace them and replace the oil pump with a reman or do it yourself.
Rod journals are easy to mic. Mains usually have the size stamped on one of the bearing shell halves. All the rules apply e.g. PlastiGage at least one main and one rod journal to make sure you received the correct size bearings, use assembly oil, don't mix up the caps, side to side. Keep the numbers matching and torque to spec. CHeck the crankshaft end play. If you bought quality main bearings that should be OK.
I take the fasteners to torque, pull the engine through a couple of revolutions, loosen the nuts and bolts a half a turn or so and retorque. Maybe just unnecessary extra work but it's the way I have been doing it for years.
Hope this helps.