I just put my 400 back together with new hydraulic roller lifters. Now that everything is reassembled I am second guessing myself. I am using regular adjustable shaft mount roller rockers. The shaft gets it’s oil supply from a hole in the shaft that is fed from the second mounting stud from each end.

My question: Is there a top and a bottom to the shaft? Is there an oil supply hole in both sides of the shaft or just one side? Is it possible to install the shaft with the wrong side up and have the oil supply hole face up with the other side of the shaft effectively blocking the oil supply from the head?