>From: L.S.Griffiths@PHYSICS.SALFORD.AC.UK

>I turn to the collective wisdom of the world...

>Is the gas cap supposed to seal like that or is there a tank vent
>that might be blocked ?  I took the cap off just to be sure.

Lee,

In this small corner of the collective the same thing
happened to me over the weekend.  The early fuel tanks had
no venting to speak of so I know of nothing that could be
blocked.

I attributed it to the cold front that had just come through
the area.  The change in temperature and associated
expansion/contraction of the fuel would (IMO) account for
the pressure.  Under most circumstances the pressure would
equalize through the cap over a period of time.  To me it's
like putting an empty plastic milk jug outside.  The air in
it cools, contracts and the jug shrinks.  When it warms up,
or the pressure equalizes through the cap, the jug retains
its shape.  Unless someone else posts a warning on this I'm
not going to lose sleep over it.

-Jim Bryant
'67 Deluxe
'67 Westy
'67 Double Cab