Survey: Original 1968/69 Corvettes w/ RC-15 cap?

[Patrick H.]

Hello All,

Working on a couple of details in finishing the RC-15 radiator cap article. I'm trying to confirm or deny the usage of a certain configuration of the RC-15 cap in 1968.

I know that the RC-15 was originally used in 1968 big blocks as well as 1969s in all applications with copper brass radiator with integral filler neck or with copper/brass supply tank.

Does anyone own a Corvette they've had either since new or since the early 70s that has an RC-15 cap on it that they think might be original? If so, could you please let me know if the rivet in the center is "flat" or "dished"?

I know what i've been "told," but it seems original unrestored 68s are not common and I'd like to see if anyone (Kurt Bunting?) has one that would qualify.

Thanks,

Patrick

[Patrick H.]

Pictures

Examples of each for your reference:

Flat rivet:

Dished rivet:

[Kent K.]

Re: Survey: Original 1968/69 Corvettes w/ RC-15 ca

Patrick,

I have an unrestored 1-previous owner '69 435hp that I will check tomorrow after work if I remember. Also, since we work at the same office, I can check with the original owner if he recalls ever replacing the radiator cap. If he did not, we're in luck.

Best regards,
Kent #6201

[Chas Henderson #28127]

Re: Survey: Original 1968/69 Corvettes w/ RC-15 ca

Patrick,
I have a very original 71 coupe (Dec 70 build) with the original cap and it is flat and copper.

Chasman

[Patrick H.]

Re: Survey: Original 1968/69 Corvettes w/ RC-15 ca

Chas,

Yes, that is correct for at least 70 and later (i.e. through 72), likely 69 and later.

The "hollow" or "dished" rivet is correct for 66 and 67. The kicker is 68. One source suggests dished rived, another flat. I'm hoping that a few original RC-15s on 68s and even 69s can help us.

Patrick

[Jim T.]

Re: Survey: Original 1968/69 Corvettes w/ RC-15 ca

Patrick my original owner 70 has the original radiator cap and like you have mentioned it the rivet is not dished. Finish on it is really in pretty good shape to be 35 years old.

[Joe L.]

Re: Survey: Original 1968/69 Corvettes w/ RC-15 ca

Patrick-----

One thing to keep in mind: it would take a very large survey of original caps of the 68-69 period to get even close to the theory that any particular rivet configuration was exclusively used during those years. The RC-15 cap was very widely used during that period. There may have been more than one manufacturing location or, if only a single plant turned out all the caps, there may have been different tooling used in the same plant at the same time (i.e. multiple lines manufacturing the caps).

[Patrick H.]

Re: Survey: Original 1968/69 Corvettes w/ RC-15 ca

Joe,

We've actually run the numbers and also looked at tooling marks on various caps. As a result, we even have theorized there may have been only one machine that did the production RC-15s at all. Because of that, it may be entirely possible that this type of rivet pattern exists.

In addition, some internal structure changed when the rivet head did, so I would suggest it's even "the way it is."

Patrick

[Kent K.]

Re: Survey: Original 1968/69 Corvettes w/ RC-15 ca

Patrick ----

I first checked with the original owner of my '69 435hp Corvette SN 726231. He did not remember ever replacing the radiator cap and was judicious enough to keep most all parts removed/replaced over the years, although, after photographing it, I believe it was replaced. It appears old enough to be the original, however it is double strike stamped 15# RC-26 and has the dished aluminum colored rivet. Were RC-26 radiator caps ever provided with '69 cars from St. Louis?

Sorry I couldn't be of more help in your research.

Best,
Kent #6201

[Patrick H.]

Re: Survey: Original 1968/69 Corvettes w/ RC-15 ca

Yes, RC-26s were used as well. They were used on applications that originally came with an aluminum radiator OR an aluminum supply (overflow) tank. Does yours qualify?

Patrick

[Kent K.]

Re: Survey: Original 1968/69 Corvettes w/ RC-15 ca

Patrick ----

It is a 427ci/435hp. If they came with either aluminum radiators or expansion tanks, then it must be the original radiator cap and correct for the application.

If you would like pictures, I'll have to send then via email if you'll send me your address.

Best regards,
Kent #6201

[Kurt B.]

Re: Survey: Original 1968/69 Corvettes w/ RC-15 ca

Patrick,
Just saw your post regarding the RC15 cap. Sorry for delay in responding. I just checked mine and the center rivet is "dished" i.e. concave.
Kurt Bunting # 26406

[Joe L.]

Re: Survey: Original 1968/69 Corvettes w/ RC-15 ca

Kent and Patrick----

All 1969 Corvettes with L-71 were originally equipped with an aluminum radiator supply tank and, consequently, all were also equipped with the RC-26 radiator cap.

[Patrick H.]

Re: Survey: Original 1968/69 Corvettes w/ RC-15 ca

Thanks Kurt.