I HAVE AN AFTER MARKET NON VENTED GAS TANK. I HAVE TRIED SEVERAL KINDS OF GAS CAPS BOTH VENTED AND NON VENTED. I HAVE PRESSURE BUILD UP IN THE TANK OR I GET FUEL SPILLING OUT OF THE CAP WHEN I EXCELLERATE HARD. HAS ANYONE FOUND A SOLUTION TO THESE PROBLEMS? THIS IS 1970 CHEVELLE WITH A 454 ENGINE
Is the gas cap located behind the license plate?
Yep.
Wasn’t there a flapper down at the base of the filler neck to stop this? I guess the aftermarket manufacturer didn’t put one in.
While it’s been (many) years since I was putting gas in these, I don’t remember a flapper. But could have been one.
You wouldn’t see it, it was at the base of the filler tube, where the tube goes into the tank. I think there was some sort of baffle too that was supposed to stop anyone from trying to siphon out any gas.
When there was a locking gas cap on my 69 Torino Cobra Jet the gasoline would shoot out like that. Switching to the regular one stopped it. Sorry it didn’t work on yours. You might have to replace the pipe.
The only solution is to install a tank with baffles in it designed to prevent sudden shifting of the gas to the tank’s rear. Or, stop doing wheelies…
The tank needs to breath both in and out. A nonvented cap on this vehicle will cause a vacuum buildup that will starve the engine. To the best of my knowledge, the tank has no other way to breath except through the cap.
1970 chevelle
…I GET FUEL SPILLING OUT OF THE CAP WHEN I EXCELLERATE HARD.
This used to happen a lot at the drag strip back in the day. One fix was to stuff the neck with a rubber ball with a bolt through it (for extraction). Mighty rinky-dink though, and not really suitable for the street.
After a buddy almost lost his car to a fire caused by this. We found a gas tank in junk yard that had ball that would plug the filler tube so this would not happen. I mounted it in his tank. When I welded in they all left. LOL. I don’t know what the tank came out of, as it was in a pile of old tanks.
It would be easy to make one like it. It was a ball that looked like a ping pong ball, mounted in a tube. Gas could go by it when filling. But if gas tied to go up the filler tube it block it.