75 Gas Cap Description

[Alger R.]

Can anyone provide the details of the inscription on the 1975 Gas Cap. The NCRS Judging Manual describes something different from my original? cap. I purchased a second 75 cap and while being identical in shape, is inscribed different from either the manual or my original.

[Garry B.]

Re: 75 Gas Cap Description

Alger, give me until this evening to get you this information from my '75. I became second owner of this very stock, 50K mile vehicle about two years ago, so I know that it is the original.
Garry
18531

[Garry B.]

Re: 75 Gas Cap Description

Alger, sorry for the poor quality picture. It says across the top UNLEADED
across the bottom GASOLINE ONLY. I didn't want to clean off the patina. I hope it is clear enough for your use.
Garry


IMG]http://i43.tinypic.com/152cd4h.jpg[/IMG]

[Garry B.]

Re: 75 Gas Cap Description

Let's try that again. Upload didn't work properly.

[Joe L.]

Re: 75 Gas Cap Description

Let's try that again. Upload didn't work properly.

Gary----


Does it have "NDH" stamped anywhere on the cap?

[Alger R.]

Re: 75 Gas Cap Description

Garry,

Thanks for the pic

AL

[Garry B.]

Re: 75 Gas Cap Description

Joe, I took a magnifying glass to it and I find no evidence of an NDH stamp. What I did find is something very interesting on the "inside of the cap". Inside being inside the plastic screw portion at the bottom that would be facing downwards into the tank.

Around the circumference of the inside I found three circles (a little smaller than a pencil eraser) with different number of spokes inside each. Under the first there is a 4, second one (moving clockwise) has a 5 and the third has a 6. Directly opposing these wagon wheel looking circles I found stamped into the plastic flat surface a 0 4 3 5. Considering my car was assembled in very early March, I would read this as March 4, 1975 correct?

Joe, where would the NDH be located if I were to find it and why do you ask?
Thanks.
Garry

[Paul B.]

Re: 75 Gas Cap Description

Directly opposing these wagon wheel looking circles I found stamped into the plastic flat surface a 0 4 3 5. Considering my car was assembled in very early March, I would read this as March 4, 1975 correct?

...I believe that was Julian dated and should be the "43rd" day of 1975, or Feb 12th to be exact from the dates I have looked at on these type '75-'82 gas caps. Looks exactly like my 167,000mi cap on my '75 coupe.

[Joe L.]

Re: 75 Gas Cap Description

Joe, I took a magnifying glass to it and I find no evidence of an NDH stamp. What I did find is something very interesting on the "inside of the cap". Inside being inside the plastic screw portion at the bottom that would be facing downwards into the tank.

Around the circumference of the inside I found three circles (a little smaller than a pencil eraser) with different number of spokes inside each. Under the first there is a 4, second one (moving clockwise) has a 5 and the third has a 6. Directly opposing these wagon wheel looking circles I found stamped into the plastic flat surface a 0 4 3 5. Considering my car was assembled in very early March, I would read this as March 4, 1975 correct?

Joe, where would the NDH be located if I were to find it and why do you ask?
Thanks.
Garry

Gary-----


Yes, I'd say the plastic casting date symbol you found decodes exactly as you have surmised.

At least some, if not all, of these 1975 gas caps were manufactured by New Departure-Hyatt, then a division of GM. Caps manufactured by them were usually stamped "NDH". However, I don't know that all were.

The problem is that there were several different caps used over a relatively short period of time in the 75-76 period. These included GM #7470051, GM #560524, GM #559346, and GM #556389. I have an NOS GM #559346 and it appears identical to your cap except it has "NDH" stamped in small font size on the top. The big problem here in identifying gas caps is a VERY common one for a lot of GM parts: NO part number is usually found on these caps.

Usually, GM requires a manufacturer's ID mark to appear on parts, except with specific authorization to delete it. That authorization was often given when the part was manufactured by an internal GM division, but not very often when the part was manufactured by an outside supplier. In this case, though, it appears that the part manufactured by an internal GM division, NDH, had a manufacturer's ID and one possibly manufactured by an outside supplier (i.e. yours) does not.

Another thing that's always mystified me: New Departure-Hyatt was once a GM division which manufactured primarily bearings and bearing-related products. Why they ever got involved in manufacturing gas caps I'll never know. But, I'll bet there's quite a story behind it.

[Garry B.]

Re: 75 Gas Cap Description

Paul, I would say that you are correct. I am more used to thinking how C1 dates are interpreted. If I recall there are other parts on my '75 with the type of dating as you described.

Joe, it is always a pleasure to read your posts. I always learn something.
Thanks you guys,
Garry

[Joe L.]

Re: 75 Gas Cap Description

Paul, I would say that you are correct. I am more used to thinking how C1 dates are interpreted. If I recall there are other parts on my '75 with the type of dating as you described.

Joe, it is always a pleasure to read your posts. I always learn something.
Thanks you guys,
Garry

Garry-----


I'm sorry, I read your #7 post in this thread way too fast, especially when I got toward the end of it. Anyway, I thought you were suggesting that the date coding was a julian-type coding. As I re-read it more carefully, I see that you are suggesting it's a day-month-year type of coding. In that case, I believe that Paul is correct; it's a julian-type coding.

However, keep in mind that these "starburst" type casting symbols can be associated with all sorts of different date coding systems. The "starburst" symbols are often found on aluminum and zinc diecast as well as molded plastic parts.

[Gary G.]

Re: 75 Gas Cap Description

Gentlemen,
I have what I believe to be the original gas cap for my 75. It has NDH stamped under the word unleaded, and the part number 7470051 on the top as well. Inside the plastic screw on the flat surface, are the numbers 0225. There is also a tiny 14 in a circle between the 0 and first 2.
I don't know if this is significant or not.

[Alger R.]

Re: 75 Gas Cap Description

The following pics are the three caps I have. Maybe none of them are correct as They dont match the comments given. The first and last pics are off of my 75. The first pic, you'll see numbers on the top 599 0308. the second cap shows unleaded fuel only but no numbers. The third pic shows no lettering or numbers whatsoever. The fourth show my original from back side and no numbers exist. Am I going wacko or what?

P1060607.jpg

P1060608.jpg

P1060609.jpg

P1060611.jpg

[Joe L.]

Re: 75 Gas Cap Description

Gentlemen,
I have what I believe to be the original gas cap for my 75. It has NDH stamped under the word unleaded, and the part number 7470051 on the top as well. Inside the plastic screw on the flat surface, are the numbers 0225. There is also a tiny 14 in a circle between the 0 and first 2.
I don't know if this is significant or not.

Gary-----


The 7470051 is the cap that I think was the first one used for the 1975 model year.

[Alger R.]

Re: 75 Gas Cap Description

Garry, Could I trouble you for a picture of the side of the cap and also the bottom side? The more I lead, the more I think that all three of my caps may not be for a Corvette

[quote=Garry Barnes (18531);393447]Alger, sorry for the poor quality picture. It says across the top UNLEADED
across the bottom GASOLINE ONLY. I didn't want to clean off the patina. I hope it is clear enough for your use.
Garry