Gas Cap - To VENT or not to VENT

[ReggieFoote]

This is a basic question I should know...BUT!!!

I have a 1950 Studebaker Champion Starlight Coupe with the original 6 cylinders engine.

QUESTION: Is the GAS CAP a vented or non-vented.

Thanks in advance,

Reggie

[Skip Lackie]

Vented. Non-vented caps did not start until the 1970s.

[StudeRich]

Avantis and '62 to '66 Larks and Lark Type Non-Wagons use non-vented Gas Caps due to the external tank venting tubes.

UPDATE: Thanks Gary Ash!

[Skip Lackie]

Whoops. Shoulda remembered that.

[ReggieFoote]

Thanks much...VENTED it is an shall be.

Reggie

[garyash]

But, 1963-66 Wagonaires use vented caps! Ever seen a tank sucked flat by vacuum as the gas got used up. Not pretty!

I had to remove the tank, seal up all the ports, and slowly add pressurized water from a hose to reinflate it. Don't do this with compressed air - very dangerous.

[jclary]

Well...vented cap or not...all tanks are vented in some way. Even in pressurized systems, venting is necessary, or as Gary has reminded us, a tank sucked flat is not a desired result. I suppose, in modern, so called "closed loop fuel systems, the venting is regulated to minimize fuel vapor emissions. In our vintage fuel systems, not only are the gas tanks vented to atmosphere, but the carburetor reservoirs as well.

Think about all the attempts to control emissions in the last several decades. First I recall was the pcv valves for crankcase venting. Next, was those goofy air pumps. Nissan, and Honda, came up with some kind of staggered two spark plugs per cylinder in an attempt to get a more efficient cleaner fuel burn. (My motorcycle has that.) Catalytic converters, to incinerate fuel that escapes, and finally, ECM (computers) to provide "real time" adjustments to optimize performance, and On Board Diagnostics to warn when something goes wrong.

I'm not certain of all the complexities of the modern fuel delivery systems, but somehow, somewhere, it does get vented.

[JoeHall]

But, 1963-66 Wagonaires use vented caps! Ever seen a tank sucked flat by vacuum as the gas got used up. Not pretty!

I had to remove the tank, seal up all the ports, and slowly add pressurized water from a hose to reinflate it. Don't do this with compressed air - very dangerous.

Does anyone have a pic of a Stude gas tank that has been, "sucked flat"? I have never seen one.

I have seen gas expand in a Hawk tank, to a point when the cap was removed the air blew out with a loud, "whosh". I have also seen that pressure nearly push off the rubber gas line connector on the bottom. The one way vented cap allowed air in but not back out. I have never seen a gas cap vented the other way. I have, "vented" them both directions myself, with a 1/16" hole drilled all the way through, or a slit in the cap gasket. With charcoal cans now, all of mine vent out through the can.

[StudeRich]

Sorry I can't say I have actually SEEN a collapsed Tank, but I sure remember the result of it.
Also, I have heard the Air Rushing in when a wrong Cap was removed from some of my Studes.

In late 1959 Dad had a New demo '60 Lark VIII straight Stick 2 Door Sedan in Williamsburg Green, that quit running about half way of the 8 Miles to Home from the Dealer, he called the Service Dept. and had it towed in, they found a defective and plugged Gas Cap which sucked the Air INTO the Vacuum with a swoosh when removed, so the dented in Tank and Cap were replaced curing the problem.