Oil Pressure Blues So ; The oil pressure drops to what exactly and at what RPM ? . It's pretty common for 235's to only have 15 +/- # off idle after they're hot and almost nothing showing on the gauge when it's idling ~ . As long as the needle comes up off the gauge's peg soon after you begin to rev. the engine that's sufficient as these are solid 1940's tech low pressure high volume oiling systems . All that being said , I'm concerned you said you hear bearing noise ~ if you can force the noise by holding it to a specific steady RPM , prop the throttle there and unplug one spark plug wire at a time until the noise stops , then you'll know which bearing / cylinder it is . Once in a while someone forgets to properly torque the rod caps down and it'll rattle a while before it lets go and ruins the engine . If you find a loose rod cap , go over all of them with a torque wrench when the engines is dead cold .
