pressurized gas tank

[DAVE]

when driving my car the gas tank builds up pressure to the point that it will whistle out of the gas cap to relieve pressure I don't think this is normal. What would cause this
Thanks

[JayRamb]

Inspect the fuel vap canister. Sounds like an evap system failure. Check all fuel lines under the hood. Even the little things check out...the outlet of fuel filter at the carb/to the carb should be at the noon position.

[IRON HORSE]

Hello Dave,
      Are you sure it's pressure .. could it be vacuum ?  I had the vent tube on the top of my tank rust shut .. I just took the gasket out of the gas cap so it could breathe .. but that's me.
                                                                                                                              Later, Iron Horse 
                                  Oh! .. by the way how is the " casualty" coming along ?

[DAVE]

I'm pretty sure it's pressure it's worse on warmer days with a full tank but I'll double check, right now it's more of a concern than a problem. the fuel filter is oriented correctly with the fuel tank return line on the top at 12 o'clock. the casualty is almost ready for final assembly I have almost all the parts I need and found an aluminum valve cover at u-pull-it think I paid $15 for it so this spring when its a little warmer and dryer out I will get to it, Apes17 is at me all the time to fix it I told we would get it going with emphasis on we. She's tired of driving her Kammback wants to drive the wagon

[carnuck]

Pull the hose off the cannister at the front that goes back to the tank and see if it's plugged.

[macdude443]

Pull the hose off the cannister at the front that goes back to the tank and see if it's plugged.

Yep.  I've removed the gas cap and connected a hand vacuum pump up to the vent line under the hood to see if I can draw air through the line.  My SX/4 vent line is plugged up along the frame somewhere.  I would not just remove the gasket.  God forbid you roll it over, the fuel will spill out.

[carnuck]

Probably collapsed/rotted rollover valve.

[macdude443]

Yep.  Time to place an order with DeLorean Motor Company.

[carnuck]

They are a few miles from me here in Seattle (actually Bellevue, WA)

[macdude443]

The DeLoreans use the same rollover valve.  I bought one as a spare a while back.