I am having vapor lock problems again and need ideas. '78 40, 2F, stock fuel tank, confirmed the lines are installed into the tank correctly, tank is clean, all vents are clear and hooked up, no charcoal canister but the line is routed up the firewall above the tank with a small filter on it, gas cap vents, clean filter, no kinks in the line, and I rerouted the stock line so it is no longer under the frame. The fuel line is either stock metal tubing or 3/8 fuel line. I installed an electric fuel pump directly under the tank with the fuel line as short as possible and still gravity fed. The mechanical pump is still installed and works until the vapor lock problem. It has been replaced three times now. Went wheeling Tuesday and the engine was a little hot and each time, the electric pump could not push the fuel unless I crawled under the truck and disconnected the line just before the OEM fuel filer. Each time a rush of air would come out and then the fuel (from the tank side, not the hot engine side on the line). The exhaust is on the other side of the truck. As soon as I hooked it back up, you could hear the fuel running all the way into the carb. I tired pulling the gas cap when it was vapor locked and blew air backwards through the vents into the tank. Any ideas?