Hi guys. My 69 Camaro has a new tank and sender and is working fine but I find it has a vapor pressure build-up that releases when I open the gas cap. I have replaced the gas cap with a new Stant one and a new GM one. Both say "VENTED" and "ANTI-SURGE" and fit well. I have double checked and these are the correct gas caps.

Is it normal for the tank to build up some pressure? If not, can you give the part number for the gas cap that you have used successfully?

Thanks!

 

Is it a lot of pressure that feels like it wants to blow the cap off, or just a little hiss of pressure? If you get a little hiss, I wouldn't worry about it.
I had replaced my old cap with a shiny new aftermarket "vented" one. After a drive, so much pressure built up inside the tank that gas was being forced past the sending unit gasket. I said screw it (or something more colorful) and put the original cap back on.

 

I agree with Camaro 69. if it's just a little "poof" when you open the cap, no worries