if the fuel lines at the carb were you disconnect is lower than the fuel level in the tank, it will syphion out.
all that stopping fuel from draining into the engine is the needle and seat.
one time i got my camaro ready to race, filled the rear cell with "good fuel", loaded the car on the trailer and backed it into the driveway, ready to go for the next morning.
The driveway was on a little bit of an angle up, so the back of the car was higher than the front. Well next morning I come out and there is a puddle of gas on the driveway under the engine. Apparently, the needle and seat stuck open, and fuel drained into the motor filling the oil pan with fuel, whcih then leaked out of the dipstick hole in the oil pan (big block)
no racing that day for me... :cry: