I can't Get A Locking Gas cap To Fit? 74' C10

[Cadillac Kid]

Hello,

I posted a thread awhile ago about not being able to find the correct locking gas cap for my 1974 C10 Fleetside Longbed. I'm pretty frustrated now about the gas cap. In my other thread I mentioned that I tried to modify the stock filler neck to accept the locking cap. (I know, this was the wrong thing to do). The cap I bought originally and still have is Stant 10572.

Today in the mail came another filler neck from a 1978 fleetside that I bought, because the stock filler neck is basically useless now. The locking cap fits in the new filler neck and stays in place if you twist it, like it should. But if you tilt the cap up and down and wiggle it, it just pops out. I feels like the width is too narrow and it is loose in the neck. So I have a new used filler neck, and still don't have a gas cap. Ive spent about 40 dollars in this issue and it is just stupid. Am I doing something wrong, or is the problem with these filler necks?? I know there are tons of people that use locking caps on these trucks, what is the secret?? If you have a locking cap on your truck and know the part number, or have a picture please let me know. I would really appreciate it!

Thank you

-Gavin

[S10Fan]

I don't have an answer on the cap. If theft is the issue, a company makes a spring that goes in the neck to keep siphon hoses out.

[S10Fan]

Classic Parts of America shows 3 different caps for 73-74, 73-78, & 73-78, I'd call them and see what's up.

[Dead Parrot]

One problem is that the 70's had a variety of emissions levels. Some could use leaded gas, other required unleaded. Optional gas doors might complicate the issue as well. Cap for a door might need to be a lower profile to allow the door to close.

At least now, you can carry your new filler neck to the parts store and test the caps in the store until you find one that works or you run out of options.

You should check that the rubber filler hoses are the same size for your existing but damaged filler neck and your just acquired one. They should be the same size but....

[Cadillac Kid]

Hello everyone. I solved my on going problem!

I spent a lot of messing around with the 78' filler neck a few days ago and I called quits. Then that night at 2:00 am I got out of bed because I knew that this was going to be the solution. The two folded in lips on the inside of the filler neck that have the little stops on the end of them (so the gas cap can not rotate 360 degrees) was the problem. Over time I guess the inside folds get worn and pushed down from use. I spent about another half hour trying to figure out how to pry up the inside folds and what tool would work. This was difficult because you can not get a tool in from the backside, and you can't get a pry bar or screwdriver in the front because the front opening of the filler neck is to small. What actually worked perfect, and what I used was one of the hook tools from a swiss army knife. It has a 180 degree bent hook that is made out of thick material, like a fishing hook but much thinker and stronger. I inserted the tool underneath the folds and twisted and lifted the folds up. The locking gas cap fits perfect now, and doesn't come out by its self. It makes sense now why this was the problem. The locking tabs on the gas cap are tapered with a flat spot on the back. The flat spot needs the rest on the inside metal when sprung down in order to not be able to remove the cap. This was the problem.

Thank you for the support. Sorry for the long response. I just wanted to try and make my self clear if someone has this problem in the future. So both filler necks had the same problem. That was very unlikely, but It was the problem.
It also doesn't help that there are many different styles of gas caps for just this range of years. Just makes it more confusing. The filler neck is back on the truck and the gas cap is in, and it locks. Perfect.

-Gavin

[S10Fan]

Originally Posted by Cadillac Kid

Then that night at 2:00 am I got out of bed

Awesome! I thought maybe I was the only one that did stuff like that! LOL

[ivorton74]

I have one on my 74...went to Napa and had them order it for me