Low Oil Pressure

I have freshly stroked 383. My son pulled the block (350ci center bolt) from an 89 Chevy passenger van. I installed a new oil pump in the build up. The engine runs fine, but I have less than 5 PSI on my new Autometer electric oil pressure guage. I put a mechanical SunPro guage on it to confirm and got no reading at all. I pulled the valve covers and there is oil getting to the heads. Although it takes a while to start flowing up there and there is very little coming out of the rockers. I have Crane mechanical lifters with Roller rockers. The oil filter fills up and oil pisses (slowly) out of the sending unit hole when running. I'm at a loss.

There must be pressure becuse my son drove the car (I was not aware of this and was pissed) all day Saturday around town and it returned running fine. I pulled the keys of course and have parked it for fear of smoking the engine.

My son (19) told me that when he was installing the engine that a chain broke and the pan got dented in the rear! Could he have damaged the pick up? Sure enough I crawled underneith and there is a decent sized dent in the bottom of the rear (deep well) of the pan.

Is there any other way to detect oil pressure? Has anyone ever encouontered this before. I'm at a loss. Can the pan be dropped to inspect the oil pump without pulling the engine or at least unbolting the motor mounts and lifting the engine? This engine is in my 91 RS.

Help!
Dave

The pan can be removed with the motor in the car, but yes, you will have to unbolt the mounts, and remove the distributer to get a clean lift up on it.