> Lee,
> 
> I don't know for sure, but I think that your older bus expects the gas cap 
> to include a vent.
> 
> I am reply quickly to this because I think that you could be creating 
> yourself quite a problem.  I believe what you heard was not pressure, but 
> vacuum.  There is a very real danger of collapsing your gas tank.  You 
> wouldn't think that a little fuel pump could do that, but trust me, it can 
> and will.  (I hope that that hasn't happened already!)
> 
> Later models have a fuel vapor recovery system that requires the gas cap to 
> seal, not vent.
> 
> The solution is to drill a small hole in the gas cap.

It might be noted that my '57 came with a small hole already drilled 
in the gas cap.  I have since procured a NOS gas cap and am going to 
stick it on when the brain reminds me to again.

Anyhow, I imagine the old busses don't have any other vent than the 
fuel filler, and probably expect some venting around the cap.

Lee, you might change the washer on the cap for a slightly thinner 
one, or go without, or cut a slice in it?  But I wouldn't recommend 
the drill only on the basis of aesthetics.

- Mike White 

[Mail: mike.white@law.utah.edu   -   mwhite@eng.utah.edu]
Visit my '57 23-Window VW BUS at: [http://fpc99.law.utah.edu/]