63 gas cap

[Michael G.]

As with almost every part on the 63 car, during the 63 model year the gas cap changed to a different design. The first cap was, I believe, vented to the atmosphere, the second was not.

I have an original on my early car, but it doesn't give me any hints of the internal construction. They're pretty rare and expensive, so I don't want to mess with it, so, does anyone know if the original cap p/n 3820865 had any sort of spring or other pressure regulator inside it, or was it just always open to free vapor escape to the atmosphere ?

Thanks,

[Joe L.]

Re: 63 gas cap

As with almost every part on the 63 car, during the 63 model year the gas cap changed to a different design. The first cap was, I believe, vented to the atmosphere, the second was not.

I have an original on my early car, but it doesn't give me any hints of the internal construction. They're pretty rare and expensive, so I don't want to mess with it, so, does anyone know if the original cap p/n 3820865 had any sort of spring or other pressure regulator inside it, or was it just always open to free vapor escape to the atmosphere ?

Thanks,

Michael------


The original, first design 1963 fuel cap had no internal pressure/vacuum valve. There was just a hole which provided venting. The second design cap had an integral pressure/vacuum valve. In addition to other visual cues, the second design cap can be identified by a very tiny "flaring" at the center hole on the bottom of the cap. Neither cap had any hole on the top surface of the cap which could be seen with the cap installed on the fuel tank.

[Duke W.]

Re: 63 gas cap

Joe - Section 8 sheet 5.00 of the AIM shows that the sheet was updated with the new cap part number on 2-22-63. My mid March SWC, sequence number just under 11000 has the vented cap. Do you have any idea when the new cap with the pressure/vacuum relief valves entered production on the St. Louis line.

[Edward J.]

Re: 63 gas cap

Duke, my mid March car is 106xx has the newer version cap. your car should have it two.

[James W.]

Re: 63 gas cap

Mike,

Is this the style of gas cap you have on your '63? This is what I believe to be an early production 1963 gas cap that I have in my parts collection.


Regards,

James West

[Duke W.]

Re: 63 gas cap

My 109xx has the same cap as in James' photo with the big VENTED stamp. As the original owner I know the cap is original. So it appears that the new pressure/vacuum relief cap was being installed at St. Louis by at least mid-March. There is always a disposition for superseded parts, and it's usually "use until supply is exhausted", unless it's a big safety or reliability issue. So there was a period of time when both caps were installed on the line indiscriminately depending how how they were pulled from inventory, and this was a very common scenario when a part was superseded with a different design, and there were a lot of these situations in '63.

[Joe L.]

Re: 63 gas cap

Mike,

Is this the style of gas cap you have on your '63? This is what I believe to be an early production 1963 gas cap that I have in my parts collection.


Regards,

James West

James------


Yes, this is the early 1963 cap.

[Joe L.]

Re: 63 gas cap

My 109xx has the same cap as in James' photo with the big VENTED stamp. As the original owner I know the cap is original. So it appears that the new pressure/vacuum relief cap was being installed at St. Louis by at least mid-March. There is always a disposition for superseded parts, and it's usually "use until supply is exhausted", unless it's a big safety or reliability issue. So there was a period of time when both caps were installed on the line indiscriminately depending how how they were pulled from inventory, and this was a very common scenario when a part was superseded with a different design, and there were a lot of these situations in '63.

Duke-----


Both the early and late style cap have the "vented" embossment. They're just vented in different ways. All Corvette gas caps through 1969 had the "vented" embossment.

[Michael G.]

Re: 63 gas cap

I have both caps here, but am suddenly unable to post any pictures... Until this gets sorted out, if somebody can give me their email, I send the pics to you for posting. Thanks.

The only visible differences between them are on the underside. Both say "VENTED" on the top surface. The first cap has only a small hole in the center of the underside, with a conical surface around it. The newer cap has what appears to be an upset hollow rivet in the center of the underside, surrounded by a small flat surface.

[Duke W.]

Re: 63 gas cap

My cap on 109XX conforms to your first description. Typical pressure/vacuum relief valves open at about1-2 psi, so you can check by applying pressure or vacuum to determine if they're installed.

[John D.]

Re: 63 gas cap

My 63, the LWC is March 2 or 3rd. Has the early style cap. Hole with no flare around it.
You have to watch the fuel caps as they can cause all kind of issues. I had a 65 FI car customer that complained his car would only run a few minutes and die. I drove long distance round trip to his house and the man was correct. I was geting frustrated and decided to check to see if there was gas in the tank. When I did I almost lost an arm as the damn cap practically blew off. Soooo much pressure.
You know who you are.
Anyhow I said. Hey Doc. Get a rag and lets put it in the gas tank and leave the cap off. The 65 FI car ran perfect and we went for a ride.
His cap was a POC rusty thing. True story. JD

[Tom D.]

Re: 63 gas cap

On April 3rd, 2016 I made a presentation to the Michigan chapter. The subject was GAS CAPS and GAS Doors (1963-1967). Some thought it was pretty good, as I had cooperation and help from David Tallenger, a long time NCRS member and restorer of mid-years. I will copy the .ppt file to anyone who asks by email to midvette@mac.com. Tom D. at 810 338 0307.