The Stovebolt Site Forums The Shop Area Engine Shop oil pressure flux

Hello all. I have had my '60 235 rebuilt recently. It is sixth over, balanced (incl clutch), Isky cam, twin carbs on a Offy, jet coated Fentons, and port and polished. My son has been commuting to the Navy base with it but three weeks after the build noticed that the oil pressure moves from 15 to 30 psi and back at all speeds. He called the builder and he claims he put in a new oil pump. As long as it doesn't go under 15, are we OK? A friend believes it may be that a pressure spring on the pump might be weak. What else could it be?

resinman,

I agree with you and your son...something is rotten in Pomona. I think the engine would last forever with only 15 pounds of oil pressure, but the thing is new and tricked out and should have much more than that.

The most obvious task would be to "prove" whatever gauge is on the truck now. If the pressure fluctuates consistently between the two values you noted, it sure would seem pump/bypass related.

If the rig has hydraulic lifters, I would make sure they are operating properly. It seems there would be only three options. The pump is actually fluctuating, the gauge is bogus or the engine has a internal leak somewhere.

If the oil pressure gauge is electric, I think I would start by checking that, maybe you will get lucky!

Don't forget to look at the oil filter if the engine has one...maybe it has a bypass.

Stuart

resinman,

{thought #2} The poor pressure could be a result of a faulty pressure relief valve or a internal leak (clearances), BUT, I wonder if it could be a suction side problem. I don't know if this happens, or how you would find it short of dropping the pan and visually inspecting the pickup, but it might be a possibility.

Stuart

I agree that the first step is to verify (prove as Stuart says) that the gauge is good. Take a known good gauge & check the pressure. What it does will determine where you go from there.

Resinman you shouldn't be having movement in oil pressure except when it is cold-higer and lower when hot. I have the same engine in my 62 1/2 ton truck and it was completely rebuilt by me three years ago. My oil pressre is 50 psi when cold then drops to 45 psi when hot with no movement of the gauge at highway speed. Something is wrong with the gauge or the rebuild. I would take it back to whoever rebuilt it and ask him to find out what is wrong.Normal pressure is no lower than 35 psi. Good hunting!!

What weight oil are you running?

Thanks guys, I am taking it back to the builder on Dec 5th. My son transferred to New Orleans so it is sitting in the driveway. I will bring up your helpful suggestions.
Thanks!

Sorry, Shop Shark, I have been away for over a week and didn't see your question. It is using 10-40 but I heard that 30wt detergent is better.
Regards, New Guy

Are you running an oil filter on this engine? Is the outlet restriction still in place? If not, too much oil goes through the filter and you loose a lot of pressure.

No, Josiah, not running a filter yet. Haven't installed it, sitting on the bench.
I noticed that it will show 30 PSI (max pressure on gauge) and then it will quickly flip to 15psi after about five seconds at idle.
Regards, Ron