I use my 77 C20 to pull my 5th wheel. I have no problems with that. The problem is that when sitting a couple days the gas runs back out of the carb. It takes a while to pump it back up. I'm thinking of putting a check valve in line between the pump and the carb. There is one on the filter in the carb but I have tried several of them and they just don't hold. Another thought is to put a loop in the fuel line before the carb going above the carb and back down to the inlet. Anyone else have this problem? What did you come up with. 77 Camper Special 454 400 trans.