I bought a 4.3 V-6 motor from pep boys back in the 90's for my SB 4-door Caprice I had. Spent the weekend putting it in, started it up and had no oil pressure. But when I primed the oil pump there was oil flowing fine.
I had to take it back out and exchange it for another one. After they looked at it, they said that there was an oil galley plug missing inside the first motor somewhere and it was thier fault so they cut me a check for 500 bucks for my labor and exchanged the motor for free. I can't remmber what brand the motor was sold under.