Decent locking gas cap

[Ken O.]

Who sells a decent locking gas cap for a 67 GMC with tank behind the seat? The last 2 I've gotten are junk and pop off if you fiddle with them in the slightest bit.

[demian5]

Good luck. I just went through this. 4 caps, and have the one I had on that sucked before i bought the other 4. Let us know what you figure out. I went through the stant catalog...

Im thinking I have a worn out filler neck. They either hold too much pressure and the cab stinks like gas and it almost blows the cap out of my hand on a hot day, or they leak gas down the side of my truck like the cap is missing. Im stuck with the cab smelling like gas for now.

[Stocker]

Not sure if your filler neck is the same as mine. My '72 K20 has a Stant #10491 from Oreilly's. No leaks, fits & stays put just fine. I used to have one from NAPA, #BK 7031113, which I believe is the same part. It lasted several years before the rubber seal finally rotted.

[demian5]

Issue is, pre-70 has no tank vent, 71 has one kind of vent, 72 has another. So 3 different caps...

[Stocker]

Wasn't aware of that.... sorry I couldn't help.

[Ken O.]

Thanks guys, these ones leak gas down the side of the cab and can fall off if you grab and wiggle it. I'd rather go back to a non-locking cap if it won't leak down the side.

[RichardJ]

From the Stant web page;

What is a "pre-release" or Pre-Vent fuel cap?

Some Stant fuel caps have a "Pre-Vent" feature. These caps are designed to allow the controlled release of any pressure that may have built up in the fuel tank, so the tank is de-pressurized before the sealing gasket is lifted from the filler neck. This dramatically reduces the possibility of any fuel expulsion from the tank to your hands or clothing.

Are fuel caps for today's cars vented?

Fuel caps have not been fully vented since the 1960's. Modern fuel caps typically have valves that relieve positive and/or negative pressure once it reaches a certain level.



I interpret that to mean that while the cap is not vented, their Pre-Vent feature, will relieve any negative pressure that will cause a problem with these old carbed non-evap systems.
I have what I think may be the same cap, but it has been on there so long I can't find any name or number. I has worked fine with no issues.

Summit Racing lists the Stant 10491 as fitting Chevy/GMC truck from 1947 - 1990

[HIGHWAY BY THE SEA]

The one that I put on my 68 I found on a 1967 Stepside in a junkyard. Curiously the key was still in the cab. I will try to send you a picture of it later and you may find one like it on eBay or somewhere. It is very solid metal with no plastic pieces and will not come off without the key.