[AROWHED]

I've always struggled with fuel cap and filler neck vent line spillage and gas tank pressure with the 65 GP. Every vented aftermarket fuel cap I have tried leaked to some degree, and gas always came sloshing out the factory vent line even under moderate acceleration. I think modern gas blended for fuel injection is very quick to atomize and build pressure, more than the vent systems were designed for with 1960s fuel.

So currently my setup is a GM factory nonvented cap with the vent nipple on filler neck welded closed...so at least no more fuel-stained license plate and rear bumper. I welded a 3/8 steel vent line through the fuel level sending unit assembly. It connects to a large steel can fuel filter that is postioned vertically, also it is above the tank and rear axle, the idea was it would act as a liquid\air seperator for fuel thats getting pushed up the vent line. From there I used the original 3/8 fuel line along the frame as a vent line, where it terminates inside the engine air cleaner to capture and burn gas fumes. (No mechanical pump, car has an electric pump, return regulator, and separate delivery\return lines ran along passenger side.)

Unfortunately this venting method does not work if tank is more than half full, liquid fuel still gets pushed up through the inline vertical filter (which I bet can hold 1 liquid cup itself), and further up the line until it spills into the air cleaner. Every time i get out of the car, I can catch a whiff of gas, and the fuel tank is under a small degree of pressure until I slowly open the gas cap. I have used compressed air to check this vent line for restriction but it seems to flow freely.

I would like to know how others have addressed their problems of fuel spillage, and excessive fuel tank pressure.

[Hooter]

I use a Stag beer can peppered with holes for vents mounted vertically inside a rear coil spring. The coil spring action acts to pump the gas back into the tank as it collects in the can. Came up with this idea at Norwalk at 3am while sleeping under the car and smelling fumes all night......

[AROWHED]

Hey thats a good idea. Now you can start perfecting one that pumps the 'fumes' out of your tent and enclosed car trailer after a long day of track food and beer.

[mike nixon]

Mike I'm thiking my car has a peice of fuel line attached to the Oe vent and ran up into the 1/4 extension from the neck. I never had issues with spillage after a new cap and I ran the **** out of mine thru corners.

Mike

[Deadhead]

Originally Posted by mike nixon

Mike I'm thiking my car has a peice of fuel line attached to the Oe vent and ran up into the 1/4 extension from the neck. I never had issues with spillage after a new cap and I ran the **** out of mine thru corners.

Mike

Correct, and I think it gets pinched over time and only lets a small amount of air or gas through at each edge where the kink does not restrict it all the way. That is how mine looked when I removed it. Was hard as a rock.

[AROWHED]

So if I understand correct you guys are saying there was another rubber line attached to that 180* metal tube behind the tailpanel...and this line ran up even higher, behind the 1/4 panel extension?

[63gpman]

Not sure if this is what you guys are talking about, but I am tearing my car down now and took a photo of how the venting is set up on my Cat.

[AROWHED]

Yes that is the factory tank vent, but on my GP it was a constant source of leaking fuel...even wore away the paint where the gas flowed out the end of tube. Strange there is no evidence of that in your photo. One thing to note: notice the crimp in the tubing...an intentional flow restriction apparently, but why?

[Deadhead]

'66 is totally different. It has a 'U' shaped deal on it that does not come up on the body like that at all. I will try to find and post a Pic.

[MPKind]

Reviving a 15 year old thread on the ‘65 fuel system. I’ve been dealing with the raw gas smell wafting up from the back at cruising speeds. I didn’t know the fuel vent design was that bad. Seeing others in the past posted about it. Basically every ‘65 has this vent line on the tail panel. It’s worked ok at times but now it’s gassier smelling than ever with the windows all open. I don’t understand how this system worked ok when new but now it stinks. Literally.

[SRGN]

Originally Posted by MPKind

Reviving a 15 year old thread on the ‘65 fuel system. I’ve been dealing with the raw gas smell wafting up from the back at cruising speeds. I didn’t know the fuel vent design was that bad. Seeing others in the past posted about it. Basically every ‘65 has this vent line on the tail panel. It’s worked ok at times but now it’s gassier smelling than ever with the windows all open. I don’t understand how this system worked ok when new but now it stinks. Literally.

Look at your rubber lines. Ethanol attacks the rubber, on my 62 the feed line was actually sucking air through the hose, even though it wasn't leaking fuel. There was a fuel smell driving me nuts, changing the rubber lines with ethanol compatible stuff took care of it.

[mgarblik]

Originally Posted by 63gpman

Not sure if this is what you guys are talking about, but I am tearing my car down now and took a photo of how the venting is set up on my Cat.

That metal vent tube in your pic is essentially how the big cars vented the tank until the charcoal canister era. Some metal vent lines had a coiled portion similar to the brake lines near the master cylinder. ALL of the vent lines like this I have seen have a crimped down little section in that metal line. The remaining hole in the crimped section is only .030-.040" in size. Over 50+ years that restriction becomes plugged up completely from internal line rust or other debris getting in there somehow. That's when all the trouble begins! I have dealt with several of these cars that were hard to fill with fuel, had excessive vapor lock, poor running hot, poor idle, the garage always smelled like gas, excessive gasket leakage at the carburetor, especially tri-power. In most cases, removing that metal line and running a wire through it to verify it's clear or blow compressed air through it solves the venting issues.

[MPKind]

The pic is not my car but it’s the same. The vent tube was off the car during restoration. New rubber hose and I recall clearing the tube back when the tank was reinstalled. I’m aware of the crimps in the line. The bummer is removing the tailpanel sucks. I’d want to remove the tube to thoroughly clean. Not easy as installed. Guessing the crimps limit fluid from dribbling out. It’s doing that now. This design must’ve worked fine when new. No one would put up with the gassy smell all the time.

[mgarblik]

I agree, but just venting to the atmosphere was normal in the 60's. Honestly, I would be concerned parking a 60's car in a garage with a natural gas hot water heater close by. I bet more than a few houses burned up from that situation.

[AROWHED]

15 years later! In 2017 I switched to a Holley Sniper, and made a gasketed removable plate that bolts into the top of tank, to access electric pump. Also added a return line fitting through top of tank. The factory fuel level float assembly's 3/8" fuel line now acts as an extra tank vent line, routed up to the floor above rear axle, with an inline filter, then goes along frame to open near rear bumper. Also welded in a baffle on floor of tank around pump to keep fuel near it, plus another baffle in rear of tank to slow the surge of fuel up the filler neck on hard acceleration. The fuel smell and leakage is over....for what its worth.

[MPKind]

That’s some impressive work. My current theory is the vent is partially restricted which could increase pressure. I know I checked it out when installed but I didn’t ream it out with a wire and Gumout. I may e able to fish the wire in thru the vent as installed and flush with the Gumout. Worth a try. This primative design had to work OK originally. So we’ll see.

[AROWHED]

While driving does your fuel gauge seem to read lower than it should...especially on hot days? The fuel tank swelling with vapor pressure pushes the tank bottom down and consequently the float drops with it. Quick test is stop and carefully release filler cap to check for pressure.

[MPKind]

Fuel gauge isn’t calibrated the best but works. It does the usual where 1/2 tank on gauge is 3/4 tank actual. I’m sure is swells some. Has to. I got fumed out last Monday driving back from a show at 70 mph. Horrible. It should just vent out fairly quick and be done but if it’s restricted it vents non stop and long after shut down. I could hear it gurgling in the vent tube. I’d release the cap. 5 min later it would pressure up again. It was a hot day but if it was working as designed it would vent out at the same rate as vapor pressure is created. In theory.