1981 F100, for my son.We re-did the truck.....Before:Now:

I have a 81 f100 with dual tanks. Had them both replaced cuz the truck sat so long. When the weather warms up fuel runs out of the front tank where the gas cap goes. When I unscrew the rear tank gas cap I hear a woosh and the front stops over=flowing. Does this make sense? Should there be some...