I disabled the fuel & ign and I cranked the motor for a few secs to build oil pressure through the engine. While cranking the oil pressure needle did not move at all. I checked to make sure the oil sending unit is plugged in and it is. I removed the sending unit and oil did come out, so I know there is some pressure. I hooked up an oil pressure gauge and cranked the motor for a few secs there is no pressure reading on the gauge. I removed the distributor and spun the drive shaft with my drill and I have oil pressure reading on the gauge. Why is it that I don't have any pressure reading on the gauge when I'm cranking the motor? Any ideas?