What sort of oil pressure should my Twenty Two have? It seems to maintain about 12 lbs at any rpm.
I'm using fresh Dello 400 15/40W.

hello bgates ,12 pound is not to bad , i have seen them run with 5 pounds:eek: ,bruce oz

bgates - The old Cat engines never relied on pressure for lubrication, unlike the later high speed Cat engines. They just relied on adequate flow .. and 5-10lb is adequate for an old gas Cat.

Cat went away from using pressure markings in the 1940's, and just marked gauges with "operating range" .. most likely, so that owners and operators did not become overly concerned about low pressure readings, and overwhelm Cat service people with unnecessary complaints.

Just about all the diesel Cat engines were fitted with new style gauges in 1951. These new gauges had an operating range that commenced at 4psi .. and which peaked at 11psi.

The previous gauges commenced at 10psi and peaked at 40psi. Concerns by owners and operators about low pressure readings (below the marked "operating range") .. at part throttle and low idle .. led Cat to produce the new guages with a lower pressure, marked operating range.

Cat advised, that the diesels were happy at 20-35psi operating pressure, with 30psi being the accepted, rated RPM, operating pressure .. and that it was acceptable for the oil pressure to fall to 4-5psi at idle.

Bearing all this in mind .. you can well imagine, that an old gas Cat, running at 1/3rd the compression ratio of the diesels .. probably doesn't even need the oil pressure that the diesels do.
As Bruce says, anywhere from 5psi upwards is quite adequate for the Twenty Two.

FYI - Here is the article on the gauge reading changes in 1951 ..

You guys are awesome. Thanks so much for the info.
I bought this Cat from an estate for resale. It hasn't been run in 15 years, but it,s running better each time I fool with it.
I've fallen in love with it and it will be hard to ever part with. I guess it's not really for resale anymore.