1962 gas cap issue

[Jack H.]

Whenever I fill the gas tank, gas will slosh out the cap until I drive far enough to use gas down probably 1/2 to 1 gallon. The cap is a new replacement. It also happened with the old cap which is why I replaced it in the first place. The cap doesn't tighten down at all. I'm at a loss. Any ideas?

[John H.]

Re: 1962 gas cap issue

Assuming it's a non-vented cap (the tank is vented, uses a non-vented cap), the cam formations on the filler neck may be worn down so they no longer cause the cap gasket to be compressed properly; replacement filler necks are available.

[Bruce Coxe]

Re: 1962 gas cap issue

Mine has that problem as well, and worried a lot about it until I read Noland Adams documentation that there was a service note about the problem, but that there was no revision in the AIM to reflect the change to a pressure and vacuum valve cap.. I just don't fill my tank all the way, and the problem is pretty much solved..
documentation is page 337, Corvette Restoration and Technical Guide, Vol 1

[Jack H.]

Vented vs non

I have a vented cap as that is what was on there. Could that be the problem with it not seating tightly?

[Gary Bishop]

Re: 1962 gas cap issue

Are you sure it is sloshing out? On my `62 sometimes if I fill it too full the gas will syphon out through the over flow / breather tube which is located in the fill area.

[Mike E.]

Re: 1962 gas cap issue

Often the issue is not at the top of the filler neck, but where it connects to the tank with the rubber hose between it and the tank. If the hose is badly dried out, not totally tight, etc., you will get plenty of fumes.
No matter what you do on this, realize that it is an issue with almost every 53-62 made.

[Chuck L.]

Re: 1962 gas cap issue

Jack, I had the identical problem on my 62. When I bought the car, it had an old non-vented dome topped cap that looked like it was from an old pickup truck. I bought an original replacement to be correct for judging, and it immediately sloshed gas out when I drove it. When I put the old cap back on, the problem disappeared! This leads me to think John Hinckley's solution is the only one that will work unless you can find an old cap that seals better. I also had a new vent hose on the tank, so I know that was not the problem.

[John H.]

Re: 1962 gas cap issue

I've been through this (and fixed it) on several C1's:

1. Get a non-vented (no valve of any kind, just a rivet) aftermarket cap (to stop the leakage through the cap).
2. Replace the old, dry-rotted filler neck hose, with the correct barriered fuel filler hose (not radiator hose); NAPA sells it by the foot.
3. Make absolutely sure the tank vent hose that runs into the filler cavity is open and not cracked/rotted; replace it - it's cheap.
4. Make sure the drain hose still exists from the nipple in the bottom of the filler cavity down through a rubber grommet in the underbody so spillage drains out on the road; 99% of these hoses are missing, so spillage dribbles down INSIDE the underbody instead, pools, and causes major fumes/odor in the cockpit.
5. Use strip-caulk all the way around the tank cover when you re-install it; that joint was sealed for a reason.
6. Check to make sure some dolt didn't seal up the large ventilation holes in the underbody below the fuel tank; they're there to continuously ventilate that compartment.
7. "While you're in there", add a dedicated ground wire from the tank sending unit to the frame.

[Michael Y.]

#8 No right turns! *NM*

[Christopher R.]

Re: 1962 gas cap issue - Expand on #4

As usual, John's got it right. That's what you need to do to solve this problem.

To expand a bit on his #4. There is a nipple glassed onto the underside of the gas fill compartment. On the under side of that drain hole in the gas fill compartment, a nipple should be attached. Many times it is missing. If so, it will allow gas that spills into the gas fill compartment to drain all over the underside of the car. That'd be stinky. The fix is to reattach this nipple and to attach a hose to it so as to direct the draining gas away from the underside of the car. I don't believe that Chevrolet used a hose there. Such a hose is hidden.

[Mike Harpster]

Re: 1962 gas cap issue

John,

Where do you get a non-vented cap for a C1? All of the ones I find are vented Stant replacement caps. BTW...Talked to the GM Heritage Center today and they confirmed the June 9th date and price.

Mike

[John H.]

Re: 1962 gas cap issue

Mike -

You have to dig a little for them - the last one I bought was at our local Auto Value parts store (Romeo Motor Parts) about four years ago; take your old cap with you, as 99% of the caps you'll find on a display rack (like Stant) are larger diameter than C1 caps. I'd give you the brand and number (it wasn't Stant), but I sent all my receipts with the car when I sold it.