Pressurized Tank

[Rich Herr]

I was having issue with detonating at WOT.  Went to drain the fuel and notice my tank was dented in.  My issue with detonation at wot was the car was staving for fuel.  The gas cap is always hard to open and has a rubber gasket around it.  The builder put a piece of rubber around it not allowing it to vent.  Does the gas cap on these car allow for venting or should they have a fuel pickup with a vent tube?  With out the gasket on cap I would worry about slosh on acceleration. You cannot view this attachment.

[roddster]

The fuel tank needs to be vented. Your tank appears to have been "sucked up". I" 'll say great fuel pump you have there.
  As far as the detonation goes, it might be related. You'll find out after the venting is remedied.

The fuel tank on 67's is vented at The fuel cap. The issue is there.

[Bob Gaines]

The fuel tank needs to be vented. Your tank appears to have been "sucked up". I" 'll say great fuel pump you have there.
  As far as the detonation goes, it might be related. You'll find out after the venting is remedied.

The fuel tank on 67's is vented at The fuel cap. The issue is there.

To add,given the typical factory vented gas cap I have never heard of or think it logical that it would be a issue of gas sloshing to a point of coming out the vent during acceleration or otherwise.  The cap needs to be vented in some way or negative issues some of which you describe can result. In a worst case situation where the cap portion has been modified for some reason to a point that it can't be reversed you can change out the cap portion of the pop open gas cap assembly with 2 screws if need be. FYI to change out the entire pop open gas cap assembly base and cap requires taken off the fiberglass tail light panel.   

[BryanT]

There is a notch on the upper side of the filler neck that is supposed to be a vent.  Maybe someone smoothed it out or the rubber on the cap maybe too tight.

[Rich Herr]

FYI.  If you replace your tank during a restoration the venting notch is sold separately!  LOL  Problemed solved.  Thanks for the photos and info.  You cannot view this attachment.You cannot view this attachment.You cannot view this attachment.