'67 Gas Cap

[Leif A.]

You never stop learning. Just received my fifth edition TIM&JG for the '67 today and on page 77, E-9-3 is a picture of a vented gas cap appropriate for this car. So, of course, I went and checked mine (as I have been doing with everything else on the car as I read this extremely informative publication, and low and behold see attached. I will order the correct cap but my question is...is using the cap that I have causing any harm?? I understand the EPA changed everything in 1970 and required the sealed cap to be used along with the charcoal canister but, again, what is the detriment if any using the sealed cap on my car.Curious minds just need to know...thanks.

[Joe R.]

Re: '67 Gas Cap

Leif,

If indeed the cap is tightly sealed you might have encountered a problem on a long run as the gas was pumped out of the tank and didn't have any air to replace the void in the tank. It could have made it very difficult for the mechanical pump to pull gas from the tank.
I doubt that it ever happened but if it did you might have heard a large relief as the air sucked in when you removed the gas cap.
A friend of mine had a 67 435 and every twenty or so miles he would stop and remove the gas cap to let the air in and kept on going. He finally broke down and purchased a vented cap.


JR

[Joe L.]

Re: '67 Gas Cap

You never stop learning. Just received my fifth edition TIM&JG for the '67 today and on page 77, E-9-3 is a picture of a vented gas cap appropriate for this car. So, of course, I went and checked mine (as I have been doing with everything else on the car as I read this extremely informative publication, and low and behold see attached. I will order the correct cap but my question is...is using the cap that I have causing any harm?? I understand the EPA changed everything in 1970 and required the sealed cap to be used along with the charcoal canister but, again, what is the detriment if any using the sealed cap on my car.Curious minds just need to know...thanks.

Leif-----


It's possible that this is a correct cap but not a "correct" cap. How can that be? Well, if the car has a GM replacement fuel tank after about November, 1970, it will be a GM #3967746. This tank has an integral pressure/vacuum valve. GM instructed that when this tank was used, a sealed fuel cap was to be used.

In actuality, you can use an original type vented cap. However, I highly recommend that the sealed cap be used. Why? Well, it will cut down on gasoline vapors wafting into the passenger compartment under certain conditions. One can always install a "correct" cap for judging and use the correct cap at other times.

How does one know if they have the tank with the integral pressure/vacuum valve? Move the fuel filler boot out of the way and look on the top of the tank about 4" to the left of the filler neck. If you see an about 1-1/2" "round thing" soldered into the top of the tank and nearly flush with the top of the tank, then one has a tank with the integral pressure/vacuum valve.

[Leif A.]

Re: '67 Gas Cap

Leif-----It's possible that this is a correct cap but not a "correct" cap. How can that be? Well, if the car has a GM replacement fuel tank after about November, 1970, it will be a GM #3967746. This tank has an integral pressure/vacuum valve. GM instructed that when this tank was used, a sealed fuel cap was to be used. In actuality, you can use an original type vented cap. However, I highly recommend that the sealed cap be used. Why? Well, it will cut down on gasoline vapors wafting into the passenger compartment under certain conditions. One can always install a "correct" cap for judging and use the correct cap at other times.How does one know if they have the tank with the integral pressure/vacuum valve? Move the fuel filler boot out of the way and look on the top of the tank about 4" to the left of the filler neck. If you see an about 1-1/2" "round thing" soldered into the top of the tank and nearly flush with the top of the tank, then one has a tank with the integral pressure/vacuum valve.

Bingo, Joe. Mine appears to be about 1" in diameter with a line through the center making it look like a very large screw head. Learning new stuff is soooo cool!! I, also, remember my '65 would vapor up the garage pretty good with it's vented cap. The '67 with the sealed cap allows very few fumes in the garage at all. Thanks to Joe and Joe R...appreciate the info...now, back to more reading and investigating.

[Paul O.]

Re: '67 Gas Cap

The cap in your photo is for a 1971 Corvette with a evap system.

[Leif A.]

Re: '67 Gas Cap

The cap in your photo is for a 1971 Corvette with a evap system.

Thank you, Paul.

[Ara G.]

Re: '67 Gas Cap

original cap will say vented, not sealed. Also, original won't have the caution label. the welds on the handle look like the same ones as on midyear caps though. I assume the underside of your cap has the small "SM" logo? ARA

[Duke W.]

Re: '67 Gas Cap

Leif-----


It's possible that this is a correct cap but not a "correct" cap. How can that be? Well, if the car has a GM replacement fuel tank after about November, 1970, it will be a GM #3967746. This tank has an integral pressure/vacuum valve. GM instructed that when this tank was used, a sealed fuel cap was to be used.

In actuality, you can use an original type vented cap. However, I highly recommend that the sealed cap be used. Why? Well, it will cut down on gasoline vapors wafting into the passenger compartment under certain conditions. One can always install a "correct" cap for judging and use the correct cap at other times.

How does one know if they have the tank with the integral pressure/vacuum valve? Move the fuel filler boot out of the way and look on the top of the tank about 4" to the left of the filler neck. If you see an about 1-1/2" "round thing" soldered into the top of the tank and nearly flush with the top of the tank, then one has a tank with the integral pressure/vacuum valve.

It's a good idea to have a pressure/vacuum relief valve on the tank. It will help prevent moisture from getting into the tank, especially if the car is stored in humid conditions. They typically release at about 1-2 psi vacuum or pressure.

If one has the replacement tank with the relief valve, I think it's possible to plug the vent hole on the bottom side of the "vented" cap with solder, epoxy, or silicone, but it should be done in a way that is hard to detect. I can't recall if the owner is required to remove the cap during Flight judging, but if so, it might be detectable.

If not, then the later tank with the valve will be advantageous, and you can use the original pre-'70 vented cap.

BTW, isn't there also an OE cap with built in pressure and vacuum relief valves? If so, what years was it used?

Duke

[Leif A.]

Re: '67 Gas Cap

original cap will say vented, not sealed. Also, original won't have the caution label. the welds on the handle look like the same ones as on midyear caps though. I assume the underside of your cap has the small "SM" logo? ARA

It does not have the "SM" logo, Ara. Also, no gasket.

[Joe L.]

Re: '67 Gas Cap

It's a good idea to have a pressure/vacuum relief valve on the tank. It will help prevent moisture from getting into the tank, especially if the car is stored in humid conditions. They typically release at about 1-2 psi vacuum or pressure.

If one has the replacement tank with the relief valve, I think it's possible to plug the vent hole on the bottom side of the "vented" cap with solder, epoxy, or silicone, but it should be done in a way that is hard to detect. I can't recall if the owner is required to remove the cap during Flight judging, but if so, it might be detectable.

If not, then the later tank with the valve will be advantageous, and you can use the original pre-'70 vented cap.

BTW, isn't there also an OE cap with built in pressure and vacuum relief valves? If so, what years was it used?

Duke

Duke------


All of the 1964-69 Corvette fuel caps have integral vacuum and pressure relief valves.

[Edward J.]

Re: '67 Gas Cap

Leif, Make sure you keep the cap as I may have some value to the 71 guys, They are hard to come by with the label still intact.

[Leif A.]

Re: '67 Gas Cap

Leif, Make sure you keep the cap as I may have some value to the 71 guys, They are hard to come by with the label still intact.

Absolutely, Ed. After reading Joe Lucia's post what I'm going to do is buy the '67 vented cap and put it on the shelf should I ever decide to have her judged. With the replacement tank that's in the car, the sealed cap is going to stay right where it is. Again, thanks for everyone's input. I'm up to page 115 in the TIM&JG. You only THINK you have an original car until...just realized my List 3810 carb is a service replacement (date code 0193). Great #1 driver, though

[Timothy B.]

Re: '67 Gas Cap

The vacuum/pressure valve on the tank is good but I assume the cap with the built in valve does the same thing.

I would think fuel smell in the garage would be the same with a functioning cap or the tank valve.

[Joe L.]

Re: '67 Gas Cap

The vacuum/pressure valve on the tank is good but I assume the cap with the built in valve does the same thing.

I would think fuel smell in the garage would be the same with a functioning cap or the tank valve.

Timothy------


I don't recall if there was any difference with respect to the fuel odor in the garage. However, I can say with certainty that there was a big difference in the amount of fuel odors wafting into the passenger compartment during driving. Using the sealed cap virtually eliminated it for me.

[Duke W.]

Re: '67 Gas Cap

Duke------


All of the 1964-69 Corvette fuel caps have integral vacuum and pressure relief valves.

Okay, so can I assume that the "sealed" cap was used beginning with MY 1970 in conjunction with the tank that has the added pressure/vacuum relief valve?

Duke