Does anyone know how the 1967 Firebird gas tank venting works? My 1969 firebird has a vent tube that is connected on the neck of the gas tank, it runs thru a metal line in the trunk then goes out of the rear tail panel behind the bumper. On this 1967 firebird the fuel tank pickup has a vent tube and a fuel line. The fuel pump only has one line available for the fuel line. The vent goes nowhere. I have no idea how Pontiac vented the 1967 firebird gas tank from the factory. Does anyone now how it was suppose to work or have pictures (pictures would be very helpful).
Thanks.........

67 and 68 birds had vented gas caps.
Sweet and simple.

What should I do with the vent line that is on the gas tank sending unit?

Some birds had a vent line from the fuel pump to the tank. My 400 did and some others got them. Not sure what qualifies which got them. Maybe only 400 and AC cars. Not sure. Maybe yours had it. Not sure with 67's.

If you have a vent line at the sending unit. You could:
A) change fuel pump to have a vent line and run line to vent
B) chane sending unit to not have vent
C) cap of sending unit vent

Pretty sure vent from pump to tank was for AC cars. Mine has it

X2 on venting through the cap on 67s Do a search on this site, there are some threads with part numbers. The repos with 'ears' do not fit correctly and are wrong for 67. I have a pic somewhere of the correct cap, let me know if you'd like me to post it.

That's not the vent line. That is a fuel return line. 400 cars had the smaller diameter return line. Just plug it on the sender. Like Harold said, the tank is vented through the gas cap

Bob's correct. I had vent in my head. Sorry for the miss-info.

You do have another option for using that return line nipple, if you want. You could add a fuel filter between the pump and carb with a 3rd nipple and run a smaller 1/4" return line back to the tank. Our '67 with 326 and a/c has the return line. Not sure what the specific purpose of this is. It may be to combat or prevent vapor lock?
Cal

It's not designed to be a fuel return line like a modern EFI vehicle. It's for vapor return only and it splits off of the fuel pump. Splitting fuel off from a filter might accidentally siphon needed fuel and send it to the tank instead of the carb causing fuel starvation.

Not to be disagreeable with you salmon38, but they make these fuel filters. I have one on my Plymouth Duster 318 with no issues. It was factory on many Mopars long before EFI. Anyhow, if this was the option selected he may as well change out the fuel pump and do it the way Pontiac designed it.
Cal

Agreed. My brother is a big MOPAR guy.

On the pump, it actually is a fuel return line, it's simply another pressurized outlet just like the main outlet but,,,,, it accesses a higher location in the pump canister. So if there is any vapor in the pump it will be purged out hence it is called a vapor return,,, however, after any vapor is purged you can be assured it will be pissing liquid fuel at the same psi as the main outlet. Of course the main outlet is sourced at the bottom of the canister for (hopefully) liquid fuel only.
Also, regarding the filters, check the Pontiac A-body's like 65-66, they had applications which used a filter with a vapor/fuel return line. So instead of being sourced at the pump, it was sourced at the filter.

Along the same lines, I am just getting my 68 350 out and fueled up yesterday, noticed that when I turned the cap there was a lot of pressure build up as I unscrewed, should this be the case? Or is there an issue with my cap no venting correctly, I believe the cap is a reproduction cap.

Thanks

Yeah, I've had that happen too. I assume there is a check valve on the vented cap so it only vents inward.