gas cap....vented or non vented?

RICH MUISE · 2014-07-04 12:28

My confusion lies in the fact that our oem tanks have a side vent tube, but when I look at "oem style" caps, most of them are vented. What was oem on our cars? Did they use both a vent tube and a vented cap?
I welded my oem vent tube shut ans installed a vent with rollover protection when I installed my in tank fuel pump, so I would like to stay with a non vented cap so I don't lose that rollover leak protection. Any problems with that?
btw, I also rerouted my vent tube for a simpler installation. It uses the same outlet above the license plate, just gets there in a more direct fashion.

Ford Blue blood · 2014-07-04 16:51

All the cars were vented EXCEPT wagons, rancheros and the delivery.

gasman826 · 2014-07-04 19:27

I think that is backwards. The wagons and rancheros were vented caps. All others were non vented caps. The fill tube is so low and in the back of the tank. If the cap was vented, gas would surge out onto the ground every time you took off. If the cap was vented, there would be no need for the vent tube system. The wagons and rancheros have no vent tube and therefore require a vented cap.

RICH MUISE · 2014-07-04 21:07

I'm guessing by "all car were vented except..." Bill was refering to the vent tubes. OK..sounds like a non vented cap is in order...cool, I saw a neat NOS non vented stainless one on EBAY...I'll see if it's still there.
thanks guys

Frankenstein57 · 2014-07-05 00:02

Gary is right, my ranchero tanks have only a fill neck, and a gas line fitting. I had this conversation today, as my cap leaks when I fill the tank. So I a as wondering which cap to order

Ford Blue blood · 2014-07-05 10:42

Sorry for the confusion, the car tanks are vented, Rancheros, Wagons and such have vented caps.

hiball3985 · 2014-07-05 18:21

Quote from: Frankenstein57 on 2014-07-05 00:02
Gary is right, my ranchero tanks have only a fill neck, and a gas line fitting. I had this conversation today, as my cap leaks when I fill the tank. So I a as wondering which cap to order

I've been fighting this on my Ranchero and have tried and ruined several caps in the process. Any replacement cap that says it is Vented is only vented in one direction to let air in, this was an EPA regulation put into effect in the early 70's from what I have researched . When mine sits in 90-100 degree weather it builds up pressure as the air and fuel expand. Take the cap off and the pressure coming out will almost blow you over and if the tank is full enough it will cough out some gas too. I have actually heard the tank oil can when the cap is removed and the pressure is relieved. I've read several posts where guys with early Ford trucks and a lot of early Chevys have the same problem with non vented systems. The solution most guys have done is drill a small hole in the cap to let it vent. That is what I have ended up doing, 1/8 hole. It's working so far after several other failed attempts on other caps.. I know, not the safest thing to do but until someone comes up with something better or I can locate an original vented cap...

John Palmer · 2014-07-05 21:32

I had a 1932 Roadster, and had a similar gas tank venting problem on that car. The 32 had a low mounted rear tank, with a "low filler" cap mounted on the rear (almost like a 57 Ford car). If you filled the tank, left it in the sun, it would expand the air pocket inside the tank and start forcing gas under air pressure out of the gas cap.

My solution was to drill and tap a hole (1/8th NPT) in the side of the boxed frame under the car. I then installed a (1/8th NPT, and Nipple End) Ford in line fuel filter like was used on the front of a Autolite carb into the new tapped hole on the frame. This served as the "filtered inlet" point for my fuel tank. I routed a 5/16" hard line from the inlet filter, up as high as possible inside the trunk, and then back down through the floor, and connected to a vent on top of the fuel tank. The high loop of the line was a air lock to prevent fuel from being pushed up the line into the fuel filter.

It worked just fine for 12 years, until I sold the car. Just another idea.

RICH MUISE · 2014-07-05 23:59

Oddly enough, the description of the caps for sale are very confusing. Looking at muliple pictures trying to figure out why a non-vented cap was exactly that and vice versa, I realized the descriptions given were almost always the same....and that the desriptions usually given were actually for the type of tank, not the cap itself. For example..when I first looked at "vented gas tank cap", I assumed the "vented"was refering to a vent in the cap, but that's not the case..it's refering to a cap for a vented tank. So, the neat nos cap I found described as a "non-vented cap", actually had a vent in it.
Is it just me, am I the only one who confuses this easily, LOL?
BTW, there is a NOS '57 Ranchero cap for sale on ebay....80.00!!

Ford Blue blood · 2014-07-06 09:11

Quote from: RICH MUISE on 2014-07-05 23:59
Is it just me, am I the only one who confuses this easily, LOL?

Not just you....there are many things that confuse me....

gasman826 · 2014-07-06 12:03

http://57fordsforever.com/smf/Smileys/default/deadhorse.gif
This is being written as a question...Isn't it common for gas caps that vent to have a built in check valve that rattles if you shake the cap?

RICH MUISE · 2014-07-06 14:09

don't know the answer to that one, but here are some pics to explain my confusion: both are described as vented..but I think only the top cap is. Just a guess, but I think the vents are a "channel" embossed into the inner piece that runs out beyond the filler neck outer dia.
The cap in the bottom two pics don't have that feature, and imho are for a vented gas tank

RICH MUISE · 2014-07-06 14:14

well, those pics are useless...too small.
EDIT..fixed them. here are pice of the neat nos cap I was hoping would work, but I think the "cutouts" on the side are actually a venting feature...just a different style than the one posted above....what do you guys think?

hiball3985 · 2014-07-06 14:43

Rich: I'm with you on the confusion, I'm starting to think a vented marked cap means it's for a vented tank and non vented is for a non vented tank just as you thought., and just the opposite of what I was thinking and all my failures with the vented caps.. I should have bought the original cap on Ebay, I've already wasted that amount on my failed experiments. My next move will be trying a non vented cap.

Gasman: Yes the newly produced vented caps have a spring and valve that rattle, the problem is they only vent in one direction. I've even tried removing the spring and valve but it still didn't let pressure out on the one I tried.

gasman826 · 2014-07-06 15:26

In 1957, nobody cared if the gas tank vented into the air. If the gas expanded too much, it dribbled on the ground. Who cared, it was twenty cents a gallon!!! I wonder if the check valve vented gas cap is the only style of vented gas cap manufactured today. Since when...1974??, all gas systems are closed and vent via a charcoal canister. If I remember correctly, way back when, on a hot day when you removed a gas cap, it could go into orbit from pressure in the tank. Even farm equipment had check valves in them so gas wouldn't slosh out.

Pressure in the tank tests the needle and seat in the carb!!!

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gas cap....vented or non vented?