Re: {Chrysler 300} Re: 1957 gas cap and tank venting

Carl,

My email acted a little screwy, so I'm not sure the following went out to you this morning:

Carl,

You have two kinds of venting on the '57. The first is a sheet metal trough that is welded to the inside of the filler tube. That one quides the tank air out as you pour gallons of gas a minute into the tank.

A critical pointer here: the '57 filler tube has no bend to it, and can therefore be shoved into the tank seal in any 360 degree position. It's important to note this filling vent trough inside the filler tube, and make sure you turn the tube to the position where the vent trough is on top. When you remove a fill tube from the tank for your restoration, that relationship is easy to be unaware of as you reinstall it. Even if you get it right on top, you will probably still get spit-back from the pump nozzle (likely from the later design of gas nozzle not being the right size for our old filler tubes), but it won't be as bad.

But regarding the venting of the tank with the cap in place, to make up for gas use or changes in the temperature of the air in the tank, you absolutely need a vented cap (with a small hole in the center of it) on the '57 models. The whoosh is not something you should have with the right cap.

Keith Boonstra

The photos you sent are not of a correct original '57 Chrysler vented cap. I can send you a photo of a correct one later today if you wish. One significant difference besides the vent hole, as I recall, is that the original cap does not have a "handle" riveted on top of the otherwise basically flat top of the cap. The true originals are hard to find a replacement for if you happen to leave one at some gas station in upstate New York. Ask me how I know.

While drilling a hole through would solve the venting whoosh issue, an original vent hole does not go straight through. The air takes a circuitous path around the fill tube gasket. Probably to prevent an open-air squirt out on a hard right turn.

I'll send a photo or two, and you can go on a hunt for the right one. In the meantime, any cap you can find that fits the fill tube, doesn't interfere with your access cover, and has a vent hole will get you by.

Keith

On Thu, Sep 15, 2022 at 2:11 PM Carl <cbilter@xxxxxxxxx> wrote:

Hi John, I agree that it seems that the cap SHOULD be vented given that the tank is not. I would think just drilling a small hole in the cap would do it. But it appears that the original factory supplied cap was non-vented – see photos of an NOS ’57 cap part # 1732416. Normally a hole would be found on the underside of the cap – don’t see one here – and the center dome on the outside will “rattle” when shaken. Cap usually marked vented as well??

Carl

From: John Grady
Sent: Thursday, September 15, 2022 12:39 PM
To: Carl
Cc: chrysler 300 club
Subject: {Chrysler 300} Re: 1957 gas cap and tank venting

Hi , I think you have that backwards— 57 requires vented cap , on dodge at least . Someone had put a non vented , on mine , way back in 1960 . It “ ran out of gAs” or “ frozen gas lines” —-all this bs ( hey it always started up after heating lines or new gas) . Caused by a vacuum in tank ! Which slowly fades out as you fix — anything!
I found out doing “ stuff “ in the woods ( Bob Segar) one winter night idling a long time , all of sudden Big Bang behind car, I jump out thought someone out there hit the trunk lid . Kind of scared !!I go to drive away car stalls = Yow !
By then I had gas in can in trunk over this stupid repetitive problem and no $ to fix it anyway .
So I get the gas , open gas filler , huge whoosh inwards but also big bang , as gas tank snapped back out . Aha
So yes , no gas tank vent on car in 57 , only .060 hoke in cap .
The internal or external pipe you see on gas fill neck only vents air back into top of gas filler pipe as you fill tank , has nothing to do with this overall tank air vent ( and also does not work well (!) —thus the big spill out all the time with auto fill ) .
Jg
Sent from my iPhone

On Sep 15, 2022, at 9:37 AM, Carl <cbilter@xxxxxxxxx> wrote:

Hey fellas,

It’s been a few years since the listserver has addressed the vented or non-vented gas cap issue on our cars. At that time we determined that ’57 used a non-vented cap, which seems to be the correct answer based on my New Yorker cap and an ebay search of Mopar part number 1732416 which was the ’57 part number. But while under my New Yorker today I could not find a vent from the tank itself, which is original. It does not have the vent tube like 60-63. It also doesn’t seem to have a vent tube in the filler pipe like ’56 has. That might explain why I get a “whoosh’ every time I open the gas cap (outflow- positive pressure). Fuel pump and drivability is not affected.

After searching listserver archives I found a reference from Ron Waters saying that 57-59 tanks are not vented; therefore, one needs a vented gas cap. But the original cap is not vented. Something does not seem right with this design.

Do you guys have any insight? Maybe I just didn’t find the vent?

Carl Bilter
’57 New Yorker coupe

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