If you have an inverted 4 stroke and use a "T" to fuel the engine then you will flood it all the time because the carb is upside down and the flow of fuel will go into the tank as well as the carb when you are refueling the plane. If you can put a line from the vent to the tank and make your fueling system a closed system, then fuel will be drawn into the tank and air back into the fuel jug so that very little fuel will end up in the engine during refueling.