I'm confused. My OE cap should allow air in when vacuum builds but the tank was vented to the charcaol canister.
So this cap
LINK is listed for a 72 Cuda, and states it's an Emissions fuel cap? ... but what does that mean? It also says
"the caps can have two different breathing systems: vented or non-vented" and
"In order to reduce air pollution as much as possible Gates supplies a special ecological cap. It is fitted with a venting valve system which prevents evaporation of harmful car fuel gases and complies with the EEC directive No. 70/221. In case of an accident the safety valve prevents fuel leaking from the tank." I agree with everything everyone posted here except you. The filler cap does not vent the tank normally. It is a pressure vacuum cap like what 383 stated above. It only vents in a emergency and does not help vent the tank. There should be a slight vacuum when you loosen the filler cap, that indicates the system is working properly and keeping the gas smell out of your garage.
You should keep the factory vent system in place, if you don't want to use the charcoal canister then connect the gas tank vent line to the engine crankcase on top of the motor at the valve cover breather.
Your "command center" should be vented back to the tank at the sending unit connected to the normal return fitting. That way you there again to keep the gas fumes out of your garage and the air.
Get a sending unit with a return fitting if you don't have one now for your command center venting.
If you vent through your cuda filler cap then you will be leaking fuel every time you step on the gas, don't be one of those guys.
Do not alter the factory tank venting system, use it it works best.
71 cars vented the tank to the valve cover breather so I am not re inventing anything, both of my cars are vented like the 71 cars were and I never smell gas ever around my cars.
Good luck with your FI install.
