1972 C10 Gas Cap

[BT Classics]

I've searched the forums and now more confused about which gas cap to use on a 1972 C10. I purchased the Stant 10623 as it was recommended in another post and it doesn't fit. Should it be Stant 10742 instead?

Took the '72 out for a ride and it died. Noticed the fuel filter was clogged with what looked like fine rust. Cleaned it out and it ran for a bit and did the same thing. It hadn't been out for a few years and had old gas. After I limped it home, I tore it apart and the gas tank developed some internal surface rust. I pulled the sending unit and the screen and brass float were completely disintegrated. Drained the tank and used a kit to clean, derust and seal the tank. Just got it all back together and it is running a lot better, but noticed the rubber in the gas cap is all broken. The cap also doesn't really tighten like it should, which led me to a gas cap search.

It is an EEC tank. However, when I traced the lines, the vent line terminates in the frame rail in the engine compartment and has a bolt stuck in it. I discovered the original charcoal canister behind the battery and nothing is hooked to it. So from my reading on here - if you have EEC, you need a non-vented cap. But if you have EEC and it doesn't vent, you need a vented cap. I bought the Stant 10623 as several people on here with '72s are running it. However, it didn't fit on my gas filler. The one I have now fits loose and looks like the one in this post but the first comment was:

It's not the right one. The correct gas cap only has the 2 tabs like the 2 shallower ones. The other long tabs are for a passenger car.

So my questions are -
Should I connect the vent line up to the charcoal canister (I have no idea if the canister is any good); take the bolt out and let it vent in the frame rail; or leave it capped off and use a vented cap?

Which cap(s) will fit a '72? (part number) I've been looking and gas caps say conflicting date ranges: 1938-1971, 1947-1970, 1967-1970, 1967-1971, 1973-1978, etc.

[Fbks_Cruiser]

I can’t answer you question about which is the correct cap or what to do with your eec but I can tell you what I did with my cap. When I bought my truck several years ago, the cap that was on it leaked. With a full tank, gas spilled out when cornering. I went to the auto parts store and bought a new one. Problem solved - for a year or so. The rubber in the new cap was crap, it deteriorated and started to leak. So, I cut my own seal from some sheet rubber I had in the garage. No leaks for several years now.

You should be able to repair your cap in the same way. A new seal should make it fit tighter.

[BT Classics]

Thanks Matt. Does the rubber have to be gas resistant because of the fumes? I don't have anything like that - just curious what I should look for to cut a new seal.

[FirstOwner69]

Originally Posted by BT Classics

Thanks Matt. Does the rubber have to be gas resistant because of the fumes? I don't have anything like that - just curious what I should look for to cut a new seal.

I got tired of replacing the cap every 5 years and cut a seal from an old innertube. It hasn't leaked for a minimum of 30 years. Of course the truck was parked in the garage for about 20 of those years. I kept fresh fuel in the tank though by syphoning and filling it with fresh gas once a year. The seal is still soft and pliable.