Inliners International Forums General Discussion Engines 235 low oil pressure

My '54 235 is running only about 18psi on the highway, about 3000RPM. This is after getting completely warmed up, about 15 miles, running about 190 on the temp gauge. Pressure looks great when cold, then slowly drops as the oil heats up. Running 10W-30. Thinking of trying 20W-50, but that is really a Band-Aid, right? This is a recent rebuild. Had all kinds of problems getting the right size cam journals, and getting the new oil pump to seal in the block.

No bad noises. Once really heated up, the idle in gear (powerglide) pressure is dang low, like 5psi at 500RPM or so. Take it out of gear and let idle go up to 1000RPM, and it gets close to 15psi.

Another odd thing: when you slow down, the oil pressure goes up. Only when the revs drop below 1500 or so on slowing down does the pressure drop below where it is at a 3000RPM cruise.

Dear Flame;

Sounds a lot like bearing clearences are to wide.

I would check the rocker assembly for leakage first however.

Then; using a quality pressure guage & a battery operated drill spin the oil pump & see what you have with SAE 30 oil @ room tempature with the side cover off.

If your block is not drilled for 'juice' lifters you could try it with them (solids) out & see if you can see/hear oil loss & each cam bearing.

If you haven't found by then It's in the "lower end" somewhere.

Good luck, John M.....

That 54 block had main brg. shims in it and needs to be set up with the proper clerances. If it is not shimmed properly you will have low oil pressure.

My engine builder spent a long time getting the right shim stock to set up the bearings to his liking.

How do I check the rocker assembly for leakage? I need to know what normal oiling looks like.

Thanks for the help.

Dear Flame;

Look for oil 'squirting out'. This can happen: (1) shafts upside down, (2) excessive rocker/shaft wear, (3)missing springs, (4)springs reversed, (5) oil line cracked/broken, or installed wrong, (6) Welch plugs leaking (shaft ends),

It's supposed to just drip out @ the bottom & slightly at the top from the oil relief holes in the rockers. Also; it should be running out the oil return in the center @ 5-700 RPM.

Now, when you "rev-it-up" to 1500 there will be an 'increase' in flow, but if you find a squirt the size of a urine stream somewhere, that's no good and your problem.


Good luck, John M......

Finally got around to looking at this.

The oil feed tube in the middle of the rocker assembly goes to what the manual calls the "oil connector". Only mine doesn't look like the picture in the manual. In the manual it has two tubes on the connector. Mine has one. It looks like someone welded up another hole on the connector where another tube would go. But, there's no place on the head for another tube to connect.

The good news, maybe: Oil was spraying out around the weld quite a bit. So, we're going to fix the weld and seal that up. I have a nagging worry about the other tube, but since there's no place for it to connect to the head will assume it will be OK.

Any thoughts before I ruin something?

The good news is, the oil pressure looks way better now. With the tube welded up that was spraying oil, I now see about 50psi on the interstate at 3000RPM. Holds about 30psi at 2000RPM. This is after running on the highway for awhile to get the oil good and hot.

Unfortunately there is a massive oil leak, but that appears to be the rear main seal, which will get fixed shortly.

Thanks for the advice, John.

Ya know, it does have fairly substantial flow out the rocker arm tops, which still bothers me. I suspect there is supposed to some fairly precise metering hole that feeds oil to the rocker assembly, and mine is too big, so too much oil is going to the rockers.