The only thing could be is the filter or what evere you did there. I would take that back apart and see what is wrong... Then I would run a pump drive and make sure I had oil everywhere before starting it. If you got to 180 you could have done damage to the brg. runing that long. I don't recommend starting any engine after rebuild with out first running the oil pump to get oil on top. If its on top it should be everywhere else.

There is nothing in the heads to stop oil presure