Here's a pic of my Spectra GM42BFi tank going into my 71 Firebird:



There are what appear to be 2 vent lines on the left and one (not pictured) in the same spot on the right. These are supposed to go to some sort of recovery tank behind the rear seat and then one would go to the charcoal canister in the engine compartment. I don't have the recovery tank or canister and am doing an ls swap. I'm sure I can cap off two of them, but I would think that one has to provide a vent somehow. What can be safely installed back there without causing too much of a buildup of fumes?

 

You definitely need a gas cap that is capable of allowing air into the tank as the fuel is being drawn down. You also need some way to vent pressure in the event that the pressure gets too high in the tank. I'm sure somebody makes a gas cap that is capable of both functions. If you can find that then you could just plug all 3 lines. I think that gas tank is setup so if you wanted to run a full modern evap system you could.

 

68- 72 Cutlass plastic vent and some fuel hose will likely do it.

 

With my 1965 Buick Skylark I just tapped into the factory system. It has worked out real well.

 

any pics of this setup/vent

 

Go to Brothers,OPG or any of the other Cutlass 442 vendors,it is just a little plastic tee with
three lines,two go to the vents on the tank,the third just vents under the car

 

I just found a pipe thread thread sintered bronze muffler and put it on some 1/4" fuel hose and ran it to the high point above the rear axle. I guess this is sufficient.

http://www.amazonsupply.com/parker-e.../dp/B003Q6CBO8