This weekend I finished my engine rebuild so I tried to run it, after a few tries I was gone check the oil pressure on engine head bolt and not even a drop. I had run the engine sometimes but not longer than 60 seconds and only retry after it cooldown if I need to guess I run it for about 8 minutes in total, is that time enough to damage something on the engine?
The oil pump is new and on the lower part of the oil system has oil on it, this will sound stupid but can be air bubbles?