I'm new to mopar products. I restored a 1934 Plymouth 4 dr. sedan and put a 1982 Chrsyler New Yorker 318 engine and trans. in it. I rebuilt the engine, bored .030 over with all new cam, cam bearings, rod and main bearings and oil pump. Everything was plasti-gauged on assembly and was well with-in factory specs. I now have a little over 2000 miles on it, but have had oil pressure problems from the beginning. At start-up it has about 40-50 psi at idle. After the engine gets hot it drops to about 30 psi at 3000 rpm and to almost zero at idle in gear. I currently am running 20w50 oil. During break-in I had lighter weight oil and the pressure was even less. I have electric gauges in the car and they showed the pressure a little higher, but I just recently installed a mechanical oil pressure gauge and it shows almost zero psi at idle in gear (auto. trans.). Anyone know if this is normal for these engines? Doesn't sound right to me. Thanx in advance for any help.

 

Having 0 oil pressure is bad. The way you're describing it sounds like it's an oil pump issue..

If i remember right, 30 or so psi at 3000 rpm is about correct. 10 psi per 1000 rpm.

 

Maybe try a different oil filter first. Then Oil pump maybe? Drop the pan and check the relief valve in the pump or try another oil pump. Use a standard pump not a HV pump Make sure to put a gasket between the block and pump. make sure the pickup threads are sealed and positioned about 3/8 from the bottom of the pan.
Another thought ? Did you install the rocker arms correct ? is the valve train getting oil ?

 

Go with a good filter such as a Wix...those cheapo Fram filters can collaspe and cause you a great bit damage...how about your idiot light is it coming on at idle..it so equipped it should be

 

Idiot light should go off as soon as the engine is started !! Should never come on at idle

 

Right you are but I think the reference was to the gauge saying no pressure at idle. If the light stays out, it is probably fine. Like mentioned 10 psi for every 1000 rpm. Idleing at 700 or 800 rpm might not register.
To the O.P. what pressure do you get when driving around?

 

When I was young and stupid I built a 390 Ford for circle track racing, and had a similar problem. I had lots of oil system mods done to the block and heads including treading the galleries for screw in plugs. He removed em all for threading but missed one during install. I too missed the open gallery and ignored the very same oil pressure performance you are describing. The engine ran as intended for about 5 laps. By the time I realized I had a problem it was to late.

A trick I learned to avoid the issue. After assembly is complete blow compressed air through the oil system. You hear any big leaks. This will blow assembly oil from the area under the feed ports, so I also pre-oil before start.

If you can get an air gun to your oil pressure gauge port you can do this test. If there is a big leak you can't miss it. I'd turn the pressure down to about 60 so you don't blow the filter apart.

 

Another thing ? did you check the bearing clearances when it was rebuilt ?