Fuel tank issue 1967 c10

[Jeff1967c10]

I started rebuilding my little red truck I replaced the sending unit that was the only thing I needed for the fuel system at the beginning finished up the paint job and they put fuel in the truck the gas tank expanded so bad that I had to repaint the back of the cab because it cracked the paint replace the fuel pump ordered a new gas tank and put on a new vented lid the gas tank is like the original only one line going in It as a nonvented tank other than the cap now every time I put the fuel cap on the gas tank starts expanding I cannot leave the cap On while it is running or sitting with the truck turned off any ideals on what I can do to salvage the parts I have already bought

[cdowns]

get yourself a good vented gascap and it will solve your problem

[Jeff1967c10]

I have about two from O'Reilly auto parts took the first one back just in case that was the problem still the same issue with second do you have any recommendations of where to get a good gas cap or a specific brand

[six7swb]

Does gas come out of your gas cap or the rubber gromit?

[Jeff1967c10]

It is not gas coming out it's just builds up so much pressure the tank swells I put on a new vented cap thought maybe I got a bad one took it back and exchanged it for another new one but it still builds up makes no sense the cap shouldn't let pressure get so high but yet it does so my only option thus far has been to leave the cap off

[swamp rat]

Does the cap or packaging say its indeed vented? or is it somebody behind a parts counter that looked up the wrong part?

[Molberg]

Has to be a fuel cap issue. If it's building pressure... It's not venting. Surprised it's not collapsing tank on longer run times... And starving for fuel

[BKSS67]

I've heard of guy's taking a small drill bit to a cap to make their own "vented" cap. It only needs a small hole to release the pressure.

It's a little unconventional but its a helluva lot better than leaving the cap completely off!

[imjeff]

The only way it could build pressure is with a FI setup, pump backwards or heat. Vented caps are to let air in, not out. What all do you have in the way of fuel setup?

[Jeff1967c10]

I was told that today's fuel has more ancho and can cause this issue thinking I may put a small hole on the bottom of the filler tube on the out side of the cab I think this May take care of it if that doesn't work I guess I could convert over to a new style tank mounted on the underside

[BKSS67]

Originally Posted by Jeff1967c10

I was told that today's fuel has more ancho and can cause this issue thinking I may put a small hole on the bottom of the filler tube on the out side of the cab I think this May take care of it if that doesn't work I guess I could convert over to a new style tank mounted on the underside

Just thinking FYI, it's always better to modify the cheaper and non permanent part. If you are going to drill a hole, drill it in the cap which you can easily replace. The filler tube is much harder to replace than a gas cap.

[imjeff]

I run "today's fuel" in my behind the seat tank every day. There is no way a tank should be under that much pressure without some recirc or plumbing issue.

[71meangreenc10]

If you narrow it down to a tank issue, why not install a 71-72 vented tank? I just had a new tank from rockauto sent to my door for less than $200. It was a good brand too. I agree with the above that under normal issues the tank should not be under that much pressure.

Smitty

[Jeff1967c10]

Th only thing that I had changed when this all started was the sending unit ordered every thing else after original tank messed up