Your question is part of my dilemma. It was my understanding that with the fuel valve on the tank turned off, when the timing cover is removed, less than a gallon of fuel should run out. The filter will partially drain and the fuel in the injector pump will drain, but it was my understanding that amount is all that should drain out. For whatever reason, multiple gallons came out of my pump. That's when I disconnected the injector leak off line from the pump and ended up draining the whole tank of fuel into a couple of gas cans.
I don't think that is normal, but I'm not sure at this point.
Tom in TN