69 fuel cap

[Greg L.]

Does the 69 fuel tank cap vent both ways? I would assume that it did so that air can replace the fuel as it is used but yet allow air in the tank to escape due to thermal expansion.

Thanks

Greg Linton
#45455

[Joe L.]

Re: 69 fuel cap

Greg-----

All original 1963 to 1969 Corvette fuel caps had both pressure and vacuum relief capability. Most 1963 models used a somewhat crude system, while later went to a somewhat more sophisticated system. In very late 1969 (approximately August, 1969), a pressure-vacuum valve was added to Corvette tank. This valve made the use of the vented cap unnecessary. However, Corvettes equipped with such a tank were also equipped with the vented cap right to the end of the model year.

ALL GM SERVICE fuel tanks sold for 63-74 Corvettes for the last 30+ years include the integral pressure-vacuum valve. GM provides instruction that when these tanks are used to replace tanks on 1963-69 Corvettes, the vented fuel cap should be replaced with a non-vented (70-74 style) cap.

For road use, I recommend that folks ALWAYS install a tank with the integral pressure-vacuum valve and use the non-vented cap. Doing this will significantly reduce the "intrusion" of gasoline odors into the passenger compartment, especially for convertibles. One can always install the "correct" cap for judging; it's a pretty simple "swap-out" and no one will ever know that the tank has the non-original, pressure-vacuum valve feature.

[Greg L.]

Re: 69 fuel cap

Thanks Joe, that's quite interesting. Do have any idea what the pressure and vacuum relief settings were? Not a big deal...just curious.

[Joe L.]

Re: 69 fuel cap

Greg-----

No, I don't. For a long time I've been thinking I was going to determine the values experimentally, but I've never gotten around to it. Like so many other things!