I have this engine and it is was just rebuilt before I bought it and had never been run. I have it in the vehicle and it fired up and sounds awesome but there is very little oil pressure. I primed the pump with a drill and ran it for about 20 minutes. I have very little oil coming out of the Pushrods. Oil pressure is at about 10 PSI.

What could be causing this?

As always you advice is very apprecated.