If so, they all seem to be crap from the get go. Ol' Roy had the same problem you describe. When removing the cap,a huge rush of air was sucked into the tank. The fuel pump was creating a vacuum in the tank because fresh air couldn't get into the tank to replace the gasoline that was withdrawn.
Anyway, I disassembled the cap and removed the little valve and spring.
Bend those two metal ears holding the plastic parts in place. Everything comes out and you can get the valve out and put it back together. That's been a couple years now and the cap works as it should.
The exact same problem occurred last week with a smaller vented cap of the same design on a '64 Fairlane I was working on. The cap was brand new.
I think The Filling Station or Jim Carter or one of the restoration houses sells a replacement vented cap that's all metal without the spring and valve that's more like the original and works properly.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
