Did you put the pressure relief ball & spring in the block before you installed the cover plate?
is the roll pin in the pump gear? did you install the gerotor (oilpump) both inner and outer?
They make #50+ @ idle.
I would not run it any more till you pull the crankcase cover and check those things, no oil circulation does bad things.
Also check as suggested if oil lines are properly routed.
Did you follow the explicit reassembly in the service manual?
