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.
