New fuel tank question

[Lee Stewart]

It sounds like your new gas tank is not ventilated through the filler neck so a vented gas cap would be required. It is equipped with a special breathing valve so that it can be used on non-ventilated fuel tanks. The valve relieves the pressure that can build up in the gas tank due to expansion especially on hot days.

[RAII4speed]

Originally Posted by Lee Stewart

It sounds like your new gas tank is not ventilated through the filler neck so a vented gas cap would be required. It is equipped with a special breathing valve so that it can be used on non-ventilated fuel tanks. The valve relieves the pressure that can build up in the gas tank due to expansion especially on hot days.

My gas cap is vented. And the tanks look the same.

[m22mike]

It is normal to see some + pressure with a anti surge cap. It will appear more noticable with little fuel in the tank after driving on warm days.
These caps are not directly vented to atmosphere . If they were you would spill gas with a full tank during take off.



Mike

[Lee Stewart]

Originally Posted by RAII4speed

My gas cap is vented. And the tanks look the same.

Have you had your gas cap tested to make sure it is working properly? I believe Jiffy Lube can do it.

[tjs44]

FYI,I put a repo tank in my 69 bird.It would build pressure in my garage that faces west in the afternoon.If I opened the"vented"cap it would have a big woosh.I had my 366 NASCAR tunnel port engine in the car,tried to start it one day and it was locked up.Pulled all the plugs and cranked it over,shot fuel everywhere.It had built enough pressure to push the gas past the needle and seats in the factory holley.VERY lucky it did not fire and push a rod threw the unobtainable block.To be safe I drilled a very small hole in the center of the cap.The vent allows air to be pulled in but not out.My factory 350 auto non A/C tank had a vent in the neck.Wish I had just kept it in the car.Tom