I have a 2003 Silverado 2500HD 6.0L, I recently replaced my engine and got the one in and set in place, I went to prime it and I pulled to the vavle covers off to see if I was getting oil to my heads and push rods and noticed it was getting there. I turned it over to see if I could see oil coming out of the push rods and there was nothing. there is also no oil coming out of my oil cooling lines either and I'm not building oil pressure. why can I not get oil to pump through my engine?