Basically the same as you would try to pull yourself out of the water on your own hair.
Venting is basically not for exhausting fume it is moreover for avoiding a vacuum in your tank to allow fuel still beeing sucked out by your pump.
Your idea would work if you would have a vented cas cap ( but than you wouldn´t need any vent line either).
So if your cas cap is not a vented one you need an external air supply to the tank.
Best way to do it is with a vent valve.
Aero Tec Laboratories, Ltd. Racing Fuel Cells - PRODUCTS - Vent Valves
INLINE BREATHER/VENT VALVE 5/16 PUSH ON
and than run the hose outside. There shouldn´t be any spill or surge .
TOM
Okay - thanks for the heads up.
With the ATL one, if you were going -6 vent line hose, which would you recommend using?
I don't really understand the difference between
-6 inline vent valve rollover only
-6 inline vent valve ss rollover nylon float
-6 vent valve roller float 200mbar
Ideally I'd like to run a hose from my vent fitting in my tank, to probably the middle of the car where the inline vent valve is, then direct my hose somewhere infront of the car)
I like the Merlin one, but since my vent is -6an, I want to just use braided -6 all the way
edit: Although I suppose thinking about it, I'm not certain why I'd want to put it inline half-way down the car. Just attach it to the tank's -6 vent fitting, then run my hose where I want it to go....