Gas syphoning out the vent/tank problems
Someplace, over at slantsix.org? There is an article on the early vents. The Barracudas (is that what you have??) Are somewhat different than the "trunked" cars
Is it possible the vent has been re-worked? The way the stock Darts / Valiants are built, it would be near impossible to spit, unless the tank is absolutely full up in the filler neck, and the inverted U of the vent is to break siphon
WHEN YOU POSE A QUESTION, please post year make and model