My take on the oiling system crossover tube for the small block
Couple of reasons. 1) I'm not a hydrodynamics expert, but I try to understand what's going on. Stock set-up is putting oil into one end of the galley. There are 4 holes being fed along the way, hopefully maintaining equal and adequate pressure and volume at the bottom of the hole (main journal). There are 8 restrictions along the way (lifters or bushings). Putting oil into both ends of the passage should reduce the oil flowing through so the oil doesn't "run past" any feed passages and equalize pressure and available volume in the galley. And available oil only has to go by four lifter restrictions at most. 2) It gives me a place to pick up oil for other places rather than bleeding it off of the mains.