Radiator Cap Redux (It's long)

[Patrick H.]

OK,

As per Tom DeWitt's request, I'm going to try to give you links and photos.

Realize that I am NOT a radiator cap expert. It all started when Terry McManmon and I discussed the oil cap article in the Restorer about 5 (?) years ago. The subject of a similar article on radiator caps came to light, and I told him I'd look into it. I took a LOT of photos, but once 1970-1972 engine suffix code stickers became my passion in early 2000, the radiator cap thing kind of died. So, I've got a lot of pictures and research...somewhere. Actually, I know where it all is, and this thread may make me work with a few others who have offered assistance, and write the article.

Also, I post this ONLY for educational purposes, and in no way is this meant in any other way. No one who knows me would ever call me argumentative, belligerent, bossy or cocky (unless I'm whipping your butt on the Sporting Clay course ) so please do not construe it as such.

For this comparison, I used three RC-15 caps. One is a reproduction. I believe I purchased it through Paragon, but I suspect the seller does not matter as to the best of my knowledge there is only one manufacturer. The second is a "real deal" RC-15 on my 1972 Bowtie car. The third is a current day ACDelco piece purchased through The Last Detail and actually used in driving. Sorry about any of the photos with regard to quality.

Note that these comments are applicable ONLY to the 3 caps I have, but I have found that they "could" (can?) be generalized to more of the radiator caps in existence. "Actual results and mileage may vary" or something like that.

Here is a picture of all 3 caps next to each other: To me, the most obvious item is the smaller rivet on the repro cap. The original cap and the current ACD cap are virtually identical in this respect with larger rivets.

On the left is the reproduction cap, on the right the original: Things to note: 1) smaller rivet on the reproduction as noted above,
2) the letters AC in the AC logo are distinctly "fatter" on the reproduction. In the original "A" there is actually a triangle formed by the 3 lines of the A, while the reproduction is more like a circle since the fatter letter obliterates the triangle,
3) the 15# of the reproduction cap appear the same size, while my original distinctly has a larger 15 and a smaller # with respect to each other and with respect to the RC-15 numbers beneath them,

The arrows:
On the reproduction, note that the arrows are closer to the wording TURN TIGHT than they are to the center depression of the cap: In addition, the lower arrow starts in the middle of the E of rEmove, and ends in the middle of the L of slowLy. It is similarly closer to the wording than towards the center.
On the original cap, the arrows are equidistant between the wording and the center depression of the cap, both the upper and lower arrow. The lower original arrow also starts at the beginning of the E and ends at the beginning of the Y.
Both upper and lower original arrows also have a triangle formed at the pointed end, whereas the reproduction has no "crossbar" of the triangle and the arrow is "open" from shaft to point.

The letters:
Overall, the font used on the reproduction cap is slightly smaller. I measured the first T of TURN, and it came out at "about" 0.2 inches tall on my original, 0.175 inches on the reproduction. The letters are also "thicker" in appearance, and the original cap has a distinct depression where the letters have been smacked into the cap. Unfortunately I found this tough to capture in a picture but it is notable when both are in hand. This depression is missing on the reproduction cap.

The bottoms:
Here are the reproduction, the original and the ACD: Note that the original and current ACD use the same "cup" on the bottom, while the reproduction has more of a, uh, teat? The reproduction also has a copper (?) metal base closest to the cap while the original and ACD are identical. The springs in the reproduction and original "turn" the same direction, and here the ACD differs.
Note that the locking tabs on the reproduction are about 2/3 the size of the tabs on the original and the ACD.

So that's WAY more than most of you wanted to know.
Again, this is provided in the interest of education.

Patrick

[Joe L.]

Re: Radiator Cap Redux (It's long)

Patrick------

There are, unquestionably, the differences which you describe between the reproduction cap and the original cap you have pictured. However, do we know that ALL original RC-15 caps were exactly like the one you have? That's the real issue here. Very often comparisons are made between a reproduction part and a PARTICULAR EXAMPLE of an original part. For some parts, particularly unique-to-Corvette parts which may be run off only one set of original tooling, any example of an original part is probably just about as good as any other. However, for a part like a radiator cap, there may have been a large number of different sets of tooling and all sorts of variations as tooling became worn. So, for an item like a radiator cap, I don't see how one can compare any particular example of an original part and say that all original parts were just like it.

What might be interesting would be to obtain a fairly large random sampling of known-original caps of a widely produced cap like the RC-15 and see just how much variation exists. Finding RC-15s in a salvage yard should not be too hard. Attributing to them the aspect of "known original" will be the difficult part. Just because it's an RC-15 does not mean that it's not a replacement made a decade or more after the car.

[Patrick H.]

Re: Radiator Cap Redux (It's long)

Joe,

As noted, based on the sampling I have done on cars from the 63-7? era (which does not, of course, include every known RC-15 cap, RC-13 cap or RC-26 cap much less others), the results can be applied througout the general production run. This many not, however, be true of the underside details as I didn't take the caps off every car I saw and photographed. Owners tend to frown on that. The font and placement details, however, have been the same in my sampling of both original and reproduction caps and my particular examples shown are quite representative of other RC-15 caps, both original and reproduction. Given that these 3 caps reside in my garage and my other photographs are on paper, these 3 were easy to photograph quickly last evening as examples. Photographing dozens of each style over a couple year period gave me some reasonable numbers from which to draw the aforementioned observations. Cars presented at Bloominton Gold, Carlisle and several NCRS meets are not the same as a junkyard but they were a very nice group of subjects and presented a fairly wide sampling.

Should anyone wish to analyze an photograph every known RC-15,13 or 26 extant, they are more than welcome to do so and let us know if they find other patterns.

Patrick

[Michael H.]

Re: Radiator Cap Redux (It's long)

Patrick,

I have a few good close-up pic's of one NOS RC-15 and also the one that was on my 66 when I bought it 20 years ago. I'm not sure if either one is dead on correct or original but I'll send or post the pic's if anyone is interested.

I see a difference in the shape of the center brass rivet on these two compared to pic's of the current reproduction. Both of these caps have the drill start that the others don't have.

Very interesting discussion. I'm learning as this goes on.

Michael

[Harmon C.]

Re: Radiator Cap Redux (It's long)

Patrick You are the man and I still say you are and expert on the caps you have and your picture taking and posting skills are great. The caps that are reproductions that have been made I would like to see the picture of the original used to make the part and the way it came out when it was finished side by side as you posted yours and we can all decide if the copy looks like the original used to make it. Tom If you could bring the sample to Carlisle you made your part from and a repo we can all look it over. Their still may be questions if you copied a real deal but I for one would like to see how close you came to what you copied. Lyle I will add that most copys of decals are way off also if the judge wants to go their.

[Joel M.]

(long) Could be wrong but

it appears that the ACD and the original that you have were tooled in an entirely different manner.

{original) -- I believe that in producing this cap that the center depression and perhaps the rivet hole only were formed/punched in the first die station. The second station probably embossed the lettering as well as blanked the outside periphery of what was to be. The third station would have drawn the "cup". In making this draw the top and edges would pucker if top not held flat with a major spring pad. In this operation the pad would tend to coin the embossments down while the drawing would stretch the material around all the edges thus thinning and somewhat minimizing/distorting the embossments along the outer periphery as is indicated in the photograph.

(ACD and repop) -- appears that cap was produced prior to any embossments being applied as there are no tool marks or flattened/distorted/stretched areas degrading the embossments on the top surface.

Of coarse, as Joe says, there could have been more than one shop making these caps with different tooling techniques for GM but one die set at one plant could have very easily made the entire years production in a day or two based on the simplicity of this part.

This is just my observation which someone may swiss cheese in a heartbeat but if it could be concluded that GM had but one supplier I would think it doubtful that several tooling techniques would be used by the sane supplier for the same end part under one roof. Sooooooo - Look for coined/flattened/stretched embossments along the outer periphery?????? Who knows?

[Michael H.]

Re: Radiator Cap Redux (It's long)

Patrick, this is the RC-15 that was on my 66 when I bought it 20 years ago. I don't know that it's the original to the car. I have a few more very close-up shots of the "AC" and the "RC-15" if anyone needs them.

[Patrick H.]

Re: Radiator Cap Redux (It's long)

Mike,

It does not appear to differ significantly from my original on my 72, other than the obvious lack of corrosion on your cap.

Patrick

[Michael H.]

Re: Radiator Cap Redux (It's long)

Patrick,

Is that a good thing? Does that mean that mine may be the original from my 66? (hope so) By the way, this pic was in black & white so the brass center looks like plain steel.

I was surprised how light the stamping was for all of the characters on the orig cap. The NOS cap stamping was quite a bit deeper. I'll try post a pic of that later. We're all pretty busy down here trying to prepare for not one, but TWO hurricanes. It's that time of year and everyone switches lawn furniture and garbage cans. I'll probably wind up with lawn furniture from some other west coast town 50 miles from here.

[Jack H.]

Finding original caps in scrap yards....

is tougher than one might think. I do a lot of yard walking and due to both current environmental legislation and pre-existing yard contracts with scrap specialists, some items tend to be removed/changed the minute cars come into the yard....

Most yards have contracts with local radiator rebuilders and those who don't pretty quickly gather the radiators and crush them for their scrap brass content. VERY often the original rad caps go with the radiators....

Gas tanks are drained of residual fuel, A/C systems are purged of R12, and other high value items are generally stripped from the yard cars (generators, alternators, starters, Etc.). So, it's not as easy as you might think to find a nice selection of used gas caps, oil caps, and rad caps out there.

But, one yard I frequent does reasonable due diligence and they put rad caps and gas caps in 50-gal oil drums for potential customer re-sale. Two summers ago, I spent a day sorting through THREE of these drums and I looked at, perhaps, 1000 original AC rad caps (as well as gas caps). Here's what I concluded.

(1) There WERE variations in the upper surface of AC caps.

(2) Some actually had the emboss highlighted with black paint filling the ID and arrow emboss.

(3) The attaching rivet came in two styles, what I call 'innies' vs. 'outies' and that's whether or not the upper rivet head was small/flat vs. larger with a center depression. There seemed to be no rhyme/reason to this difference and some of our Judging Guide books point out either style is acceptable. Such typically results from multiple manufacturing site locations using slightly different assy tooling.

(4) ALL of the original, from the era, AC caps had the 'cup-style' pressure relief mechanism and the later version (what I call a 'squashed ellipse') didn't begin to show up until you got to service replacement caps (SS top cap embossed 'Summer/Fall').

(5) I didn't look specifically for differences between the size of the locking ears, nor did I check the length of the locking tabs or the alignment of the top font w.r.t. the direction arrows.

(6) I DID come across a handful of the 'impossible' RC-15 caps though--those with the 15 emboss on the opposite ear from what we're used to seeing. What donor cars these came from originally, I can't say.

My hat's off to Pat for taking the time to post a nice 'teaser' thread without drawing hard conclusions on what's 'right' vs. 'wrong' and giving us pictorials! One further comment....

If memory serves, as a GM Licensee, you get access to as many original drawings as you can think to ask for along with the residual of existing tooling and supplier contacts. I spent some time at Paragon when Richard Fortier was still in charge and was invited to observe his efforts to re-tool mid-year Corvette rear bumpers.

He pointed to a STACK of GM drawings (maybe 2-4 feet tall) as we watched two of his summer hire high school/college employees 'testing' a run of first article bumpers from his supplier. They were de-mounting the factory original bumpers from Dick's untouched '65 FI car and test fitting the TWO un-chromed 1st article bumpers he'd received from his supplier. Did they fit? A first order run of something like 1000 bumpers was riding on the acceptance 'test'....

I kind of freaked out having been an engineering vice president before I retired. I asked, "Who's gone through the stack of drawings laying on the floor? Why are they test fitting the bumpers to the car instead of using micrometers and doing physical measurements against drawing spec? Why is your 1st article acceptance based on a small sample of TWO bumpers only and why aren't some chrome plated to assess that aspect of the supplier's quality?"

Dick told me he didn't have a staff of engineers to wade through the drawings (couldn't afford the overhead based on his small run business). He'd simply won the GM license contract, gone through the files to find the last known source of supply and cut a deal for a resonable number of bumpers based on their last shipment to GM.

I pointed out there was a wealth of information in the drawing files. They'd document running changes over time and maybe there was a need to make two or perhaps four versions of the bumpers specific individual time periods. Further, perhaps the company couldn't afford to have staff engineers to do this grunt interpretation work, but there were a jillion retired auto engineers in Michigan and I'd just bet you could find skilled folks willing to work on a 'contract' basis out of retirement and/or a modest royalty arrangement.

Bottom line, while licensees ask us to tell them what's right/wrong, there's a LOT they can do pour over the wealth of information available to them and help us understand! Reverse engineering, in any form, has its pitfalls because we don't see the whole picture, just like Joe Lucia says....

[Terry M.]

A machine

Sometime between 1964 and 1969 I saw a fully automated radiator cap producing machine set up at a machine tool show in Chicago. I can't say it was producing AC Delco caps though.

It was the marvel of the show because it was fully automated. Galvanized sheet stock, brass sheet stock, steel and brass wire, rolls of gasket material, and all the other raw materials went in one end. Out the other end came finished caps at the rate of about one per second. They gave away the finished caps to attendees. I can't recall the name of the company that had the machine there - no doubt it was the machine's manufacturer. Over the course of the show it produced a lot of caps though.

[Peter L.]

Re: Radiator Cap RC-15

Michael - Looks just like the original one on my '66 Chevelle w/ C60. One other key to being original to '66 and '67 and probably into '68 and maybe somewhat later from my experience is that the large thin washer that is directly under the cap and is in contact with the top of the filler neck when installed was brass while later production RC-15s had a stainless steel washer even though the information stamped on the top of the cap was basically identical. Obviously not detectable unless the cap is removed but if one claims it to be original to "the car" as we all know there can be unique features in items that were used over long periods of time like the RC-15. BTW, the RC-15 radiator pressure cap was first used in 1957 on Buicks, Olds, and Pontiacs and then in the '60 on numerous cars with air conditioning. And keep your head above water. Pete

[Michael H.]

Re: Radiator Cap RC-15

Peter,

Thanks for the info. I just looked at the original cap and it does have the large brass washer that you described. In all the years that I've had that cap, I didn't notice that washer was brass. Just assumed it was stainless steel like most new caps.

Another part that is brass is the small dime size cup/valve on the bottom center of the rubber seal. Would this be unique to these caps also or was that common to all from that era?

We really dodged a bullet on hurricane Charley this afternoon. That boy was headed directly at us but at the last minute it turned east and went inland. Good thing because the only car that I couldn't move was the 66 conv. It would have been trashed sitting in the garage with 15 feet of storm surge water coming in.

Michael

[Thomas D.]

Re: Radiator Cap Redux (It's long)

I think we have good dialog going here and maybe this will help people realize the possibility of multiple "correct" caps.
Patricks photos and Michaels show me a lot. As I suspected a long time ago, the tooling was newer in 1966 and the letters were narrow because the stamping tools were sharp. As time went on and millions of caps were stamped, the dies were re-faced, and the letters got fatter in the process. The cap that we offer right now looks to be exactly like Michaels 1966, inlcuding the hollow rivet. Actually we have both the solid rivet and hollow rivet, which Jack confirms existed.

[Michael H.]

Re: Radiator Cap Redux (It's long)

Tom,

I'll post a few close-ups of the stamping if that would be of any help.

Michael