1970 Gas Cap Question

[Carr C.]

The new 4th Edtition '70-'72 TIM & JG states that the gas cap is "dull cadmium", but does not state if it is clear cad (silver) of yellow cad (goldish).

What is the correct color of cadmium plating?

Thank you!

[Stephen B.]

Re: 1970 Gas Cap Question

I believe it's suppose to be goldish. My well worn original cap has some gold remaining on the edges. The rest of the cap is silver, but I believe the gold wore off years ago. Maybe someone with more knowledgable can confirm the color.

[Chuck S.]

Silver *NM*

[Donald T.]

Re: 1970 Gas Cap Question

Carr,

The 1970 gas cap is unique to that year. It is a zinc plated sealed cap. The 71-74 caps, which became the service replacement cap for 70-74, where zinc dichromate. Here is a pic of an original 1970 gas cap.

[Stephen B.]

Re: 1970 Gas Cap Question

I guess the edges of my gas cap were stained dark gold by years of gas or something.

[Joe L.]

Re: 1970 Gas Cap Question

Stephen-----

Does the cap have a "scalloped perimeter" or does it have a perfectly round and regular perimeter? If it's the latter, then it's NOT an original 1970 cap, although, as always, if the car were a very late 1970 I would not rule out the possibility that it was originally equipped with the 1971 style cap.

The 1970-only cap, GM #3974743, was a more-or-less "dull" cadmium or zinc with a "scalloped perimeter" (finger holds), and, most notably, a RED and white label which read "OPEN SLOWLY" "CAUTION". This was also a SEALED cap. What most folks describe as "dull" silver finish was not always as "dull" as it may appear in used pieces or, even, NOS pieces. Zinc or cadmium OXIDIZES regardless of whether it's used, or not (unless it's stored in a vacuum and few pieces are). However, the zinc or cadmium plating of old did have a more "satin" finish as opposed to the more "glossy" finish most platers apply in "more modern times".

Pictured below is a GM #3974743. Don't pay too much attention to the finish, though, except to discern that it was "silver". This is a well used example and it's been exposed to more of the elements than just air.

[Terry M.]

Re: 1970 Gas Cap Question

1970 and early 1971 (with the red and white label attached) were dull silver cad. I believe, but stand to be corrected, the later 1971 (with the caution note embossed in the cap) received the gold dichromate wash.

[Donald T.]

Re: 1970 Gas Cap Question

Here's a pic of an original 71-74 gas cap with the zinc dichromate finish (one of my restoration projects).

[Joe L.]

Re: 1970 Gas Cap Question

Terry----

I didn't know that the "scalloped perimeter" caps were used for 1971. However, as always with this sort of thing, I could understand that they were. Functionally, they were equivalent. In any event, the 1971 style cap (the one used on, at least, most 1971 models) had not only the embossed caution script and "gold" irridite overplate, but it also had the "smooth, round" perimeter, not the scalloped edges.

I thought that all 1970, except possibly very early, had the red and white caution label?

[Stephen B.]

Re: 1970 Gas Cap Question

Here's a pic of my cap. It's scallopped but does not have the red and white label. It looks like Don's cap. Are both of these caps original 1970?

[Chuck S.]

No Label in 70 *NM*

[Joe L.]

Re: 1970 Gas Cap Question

Bunky-----

Yes, this is the 1970 style cap. Also, I don't see any evidence, at all, that it was ever finished with an irridite overplate. It looks very "silverish" to me.

I always thought that most 1970's had the cap with the red label. After a bit more research on the subject, though, I think that I am incorrect and I think I see what happened here. There were actually THREE caps over the 1970-71 model period and not TWO. From what I can tell, the 3974743 was the cap used for 1970 and, MAYBE, VERY early 1971. I doubt the latter, though. It was the cap with the "scalloped perimeter", satin silver finish, and only the word "sealed" embossed on the cap; no red and white label.

Most likely, from the start of PRODUCTION for 1971, the cap used was the GM #3983384. I think that this is the cap which is the same as the GM #3974743 EXCEPT for the red and white label. I think that the 3983384 was used for a very short period of time before it was replaced by the GM #3994339. The latter is the "smooth round" perimeter cap with all lettering embossed and with an irridite overplate.

[Joe L.]

Re: No Label in 70

Chuck----

Yes, I think I've got that figured out now. See my most recent post above.

[Lyndon S.]

Re: 1970 Gas Cap Question

Terry

when you say early 1971 about what range in numbers, say up to 4500? had the silver then they went to the gold?

[Chuck S.]

Sorry, Joe...

I don't get many opportunities to answer a question for the great Karnac of Corvettes, Joe Lucia. LOL

Say, how did you figure that label question out that quickly?...Did you put an envelope to your forehead? It probably took me ten years to figure out that original 70 caps were silver and embossed SEALED.