priming the oil pump

Not sure if you can see down through the head see if the tappets are bleeding oil. This possibly of the bearing being installed improperly, should have been visually confirmed when they were installed. You are going to have to start digging to find out, no free lunch here. Yes, you probably will have to pull the intake, and more. I forgot the rear inner screw in plug on the driver's side of my 318, and yes, I had to pull the engine to install it. So get ready to do what you have to do.
Sorry.