For the past ten years and 40K miles, my 1951 216 has always registered a somewhat lower than normal oil pressure reading. Over the years I have replaced the main bearings, the oil pump and the oil distributor valve. My eventual conclusion was that the cam bearings must be really worn. Well I just put the motor back in my truck after rebuilding it with .040 pistons, etc. The oil pressure readings haven't changed. So I hooked up a gauge from my spare 1938 cluster and the pressure gauge in my truck is reading quite a bit lower than the spare gauge. So I have a new gauge for my truck ordered and on the way!