The Stovebolt Site Forums The Shop Area Engine Shop Oil pressure

I got my 52 3100 running now after it sat in a corn crib for 30 years. It has a 1954 235 engine. I took the engine apart and replaced the main bearings. The connecting rod bearings were OK. I checked them all with plastigage. It has the original 30 psi oil pressure gauge and I wasn't sure how accurate it was so I also hooked up another gauge I got from NAPA. I have 10W30 oil in it. When I start it the pressure is 50 psi at idle. When it is warmed up the pressure is about 25 psi at 50 mph but drops to around 5 or 10 at idle. Is this OK? Would 40 weight oil be a good idea? It has an oil filter which I disconnected but that did not seem to make much difference. Any advice is appreciated.

Don't worry about the low pressure at hot idle. Most modern "idiot light" switches turn the warning light on below 7 lbs. of oil pressure, but there's just not a gauge to let us see how low the hot idle oil pressure is going. If the gauge is not dropping to zero at idle, and/or there's a knock, don't get too concerned about a low reading. Heavier oil will stress the distributor gear and drive tang on a cold start, and thick oil won't lube well until it warms up a little. Personally, I'd run 15W40 or a straight 30 weight high detergent oil, but opinions about oil are like "noses" everybody's got one, and some of them are pretty "smelly"!
Jerry

I put in 15 40 oil and now the oil pressure stays at about 10 psi at idle and warmed up. Thanks for the advice.

But isnt that a 40psi oil pressure engine? The 54 was unique in that it had higher pressure than the 235s from 55-62. Something isnt right.

It's right- - - -all engines lose some oil pressure when they're hot. Unless he put a brand new high volume oil pump in during the rebuild, low pressure at idle is not a problem. Or, at least it's been that way since the mid-1950's when I started paying attention to such things. People can worry themselves into a frenzy about dropping a little pressure at hot idle, or just get over themselves and accept it. Your choice!
Jerry

Yes, I'm with you Jerry, but is the only place he checked his oil pressure at HOT idle? You depress the accelerator and watch to see what happens? What am I missing? I don't know about you, but if my oil pressure at idle was 10 pounds on a 45 pound normal system, I would push on the accelerator to see what happens?

Try it when its cold Bob. At various RPMs. Then if you see the 40 pounds on a regular basis, you are good to go. My 261 gives me 30 pounds (normal) all the time. If it ever drops below that, I am right here asking the experts. Hasn't happened yet.

I think I am OK now with the 15w40 oil. With cold oil I have 50 psi regardless of RPM. With hot oil I have 10-15 at idle and about 25 at 50 MPH.