I was just really looking at the oil flow in that diagram and it is kind of stupid the way it flows, right side oil passage, around the back to fill the left then up to the left rocker last!
I didn't realize big blocks oiled both sides from the same bearing. SB oil one bank fron #4 cam bearing and the other from #2 (I think). The IH engine in my Scout oils like a small block. Took quite a while to prime it completely.