[dpoltzer]

My 1969 FB with a 400 and a 4speed is getting a new gas tank, fuel lines and fuel pump as these items were not present when I bought this car which was mostly dis-assembled. My question is: should I order a new tank, pump and lines "with" a vapor return system or can I do with out these items? Advice appreciated.

[dpoltzer]

I just went ahead and ordered parts for a Vapor return line. Figured it would help.

[Shiny]

As I understand, the intent is to reduce risk for vapor lock by eliminating risk for trapped vapor inside the mechanical pump. I don't know if anyone could predict if you will need it but it cannot hurt and was there for a reason so I think you made a good decision.

[necdb3]

Do any of the reproduction tanks have the vent on the filler neck?

[dpoltzer]

The tank I just received does not have the vent on the filler neck.

[nashcar]

Ten years ago I had to add mine. As to the fuel line, my original 400 four speed car had the two lines and the return or vapor line had a plastic restrictor in the line near the rear. I don’t know it’s purpose but I put it in the new line when I restored the car. If anyone knows what it was for I’d like to know.

[north]

The vent fitting on the filler pipe and the vapor return line are two unrelated things.

The vent fitting on the filler pipe was initially used on all 69 Pontiacs except wagons. A hose on the fitting would be routed up a few inches and then make a 180 degree turn to vent the tank without spillage. This would allow air pressure in the tank to escape as the tank heated up or inversely as it cooled and/or as the fuel was pumped to the engine. This prevented fuel spray when the cap was removed or cavitation and tank collapse. But the small free area on the tail panel-trunk floor of the Firebird apparently resulted in many issues of pinched hoses that could cause the above mentioned problems. So mid year the vent fitting was deleted on Firebirds and instead and anti-surge fuel cap (as used on wagons) was instead installed. These caps aren’t great, especially on a car like a Firebird with a very low fill point, spills on steep uphills or under acceleration were common. Worse was that owners who lost a cap would replace them with unvented caps (not aware of the mid year change in specification) and subsequently their car would stall due to vacuum in the fuel tank or even under certain high rpm conditions collapsing the tank! This was a real half-ass solution that Pontiac came up with for the kinking vent hose issue.

The fuel return line was used on all pontiac models with a V8 that had a 4 bbl and/or AC. This system used a 3/8” fuel line with a 1/4” return line. For all 6 cylinder cars and non AC 2bbl V8’s the fuel line was 5/16” with no return. Therefore fuel sending units and fuel pumps were specific to these two possible applications.

[Sport69]

No you don't really need it, just make sure you're using a vented cap. I did have some trouble with mine vapor locking, I add insulation to my fuel lines and it hasn't been a problem since.

You can see the fuel line insulation in the picture of my engine compartment. Since the pic was taken, I've gotten rid of the glass fuel filter and went with a metal one.

[dpoltzer]

I did purchase the vented cap and the 1/4 vapor return line. Thanks everyone.