Be sure your oil pressure gauge line is on the "upstream" side of the line to the filter, the one that's attached to the gallery in the side of the block that's about 4 inches above the oil pan rail. It will be slightly above and ahead of the coolant drain petcock . The oil port down low just above the oil pan rail is the "output" line for the filter, and it carries the reduced pressure downstream of the oil distributor on the way to the rocker arms on a spray-oiler engine. If you attach the pressure gauge line to that port, you'll get virtually no reading.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!