How do you prime a Chevy big block?

I assume you are talking about the oiling system. They make a tool for such an operation. It is a long shaft, that looks like a standard screwdriver on one end, and goes into a 1/2 drill, on the other. This shaft goes down the motor where the distributor would go, and matches up to the oil pump drive. Pump the oil up until you have oil comming out of the pushrods, and the rocker arms. Your oil pressure gauge in the car will also be an indicator.