Small block radiator cap

[Jeff S.]

('66 327) Should there be a gasket of sorts under the cap's cover? I've seen RC-15 & RC-26 examples with just the stainless disc, others that have a ring of gasket material. Understand the LICS RC-26 repro is closest to original; their online catalog photo shows a gasket. Thanks in advance.

Jeff

[Edward J.]

Re: Small block radiator cap

Jeff the cap should have a gasket.

[Bill L.]

Re: Small block radiator cap

Hi:

Here are two photos with some good info about the caps for a small block:

The cap on the left is the correct cap (reproduction on the right):

Note major difference in the indentation -- the rivet, configuration of the ears, the arrows and the placement of the numbering --- very different from original to repro.

Screen Shot 2015-06-24 at 4.42.48 PM.jpg

Below, again, the original is on the left and the repro on the right:

Note the gaskets and also the difference in the retainer ears from original to repro.....

Screen Shot 2015-06-24 at 4.43.21 PM.jpg

Hope this helps a bit.

Regards
Bill

[Jeff S.]

Re: Small block radiator cap

Ed & Bill

Thanks for the reply. The repro in Bill's photos has no gasket under the cap; just the stainless disc. From the top photo, it also seems like the rivet cavity on the 'correct' cap is larger in diameter than the repro. Perhaps that's another feature/difference?

Jeff

[Larry M.]

Re: Small block radiator cap

Ed & Bill

Thanks for the reply. The repro in Bill's photos has no gasket under the cap; just the stainless disc. From the top photo, it also seems like the rivet cavity on the 'correct' cap is larger in diameter than the repro. Perhaps that's another feature/difference?

Jeff

I have personally seen two distinctly different original/vintage RC-26 caps, and (at least) 3 distinctly different RC-26 reproductions. So......there will be all sorts of differences between them....depending on which ones you have.

The two original caps were made in different years by AC so that likely explains the differences. These differences were mainly in the location of the AC, the RC-26 and the 15 #. They both/all had the extra gasket shown in the pics by Bill Lucia.

The LICS reproduction cap is closest to originals that I have seen. I bought one a few years ago, and tested it before installing using a new Stant Radiator Tester. Cap did not relieve pressure until around 21-22 psig. I did not use it for that reason, since my old, original radiator and heater core probably couldn't take the extra pressure. So if you buy one from LICS (or anyone), test it first.

The reproduction shown by Bill looks like the one I purchased many years ago from Paragon. It works beautifully, but looks a bit off from known originals.

I finally just gave up and had my original cap rebuilt by Joe Perri in Chicago. It looks very nice and works very well.

PS: I do not believe that original RC-15 caps have this extra gasket.

Larry

[Joe L.]

Re: Small block radiator cap

I have personally seen two distinctly different original/vintage RC-26 caps, and (at least) 3 distinctly different RC-26 reproductions. So......there will be all sorts of differences between them....depending on which ones you have.

The two original caps were made in different years by AC so that likely explains the differences. These differences were mainly in the location of the AC, the RC-26 and the 15 #. They both/all had the extra gasket shown in the pics by Bill Lucia.

The LICS reproduction cap is closest to originals that I have seen. I bought one a few years ago, and tested it before installing using a new Stant Radiator Tester. Cap did not relieve pressure until around 21-22 psig. I did not use it for that reason, since my old, original radiator and heater core probably couldn't take the extra pressure. So if you buy one from LICS (or anyone), test it first.

The reproduction shown by Bill looks like the one I purchased many years ago from Paragon. It works beautifully, but looks a bit off from known originals.

I finally just gave up and had my original cap rebuilt by Joe Perri in Chicago. It looks very nice and works very well.

PS: I do not believe that original RC-15 caps have this extra gasket.

Larry

Larry and Jeff------


There's a 3rd version of the RC-26 which uses a stainless steel shell with small ears. This was a SERVICE-only piece, never used in PRODUCTION on a Corvette.

The gasket between the shell and the filler neck was used on RC-26 caps. It is part of the anti-galvanic corrosion properties of the RC-26. I don't think the RC-15 used it, either.

[Ed S.]

Re: Small block radiator cap

I suspect NOS RC-26s are non existent - or a totally cost prohibitive. That said, does anyone carry a reproduction RC-26 that will pass judging?

[Larry M.]

Re: Small block radiator cap

I suspect NOS RC-26s are non existent - or a totally cost prohibitive. That said, does anyone carry a reproduction RC-26 that will pass judging?

The LICS reproduction is as close as it gets. A good judge will notice, however, and probably deduct a few points.

Rebuilt originals are probably a few hundred dollars. About 1/2 to 2/3 this cost to rebuild a good core if you have one.

Larry

[Timothy B.]

Re: Small block radiator cap

IMO,

Look for a service replacement RC-26 with the stainless shell like Joe describes above and use it while you search for a original. Don't get the one made in India, get the cap with AC stamped in the shell.

My experience with the reproduction caps is they are junk, I had one that tested 17-18 lbs relief while the original still tested perfect.

[Ara G.]

Re: Small block radiator cap

I suspect NOS RC-26s are non existent - or a totally cost prohibitive. That said, does anyone carry a reproduction RC-26 that will pass judging?

Not really. We can tell. Try and find a good original core and have it rebuilt/restored. Also, note that known original RC 26 caps have been known to have the RC 26 and the 15 lb stamping BOTH vertically stamped as well as horizontally stamped. ARA