'68 L79 radiator cap question - NCRS Discussion Boards

'68 L79 radiator cap question

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  • Dave F.
    Expired
    • December 1, 2003
    • 508

    '68 L79 radiator cap question

    I believe the correct cap for my L79 (non-air conditioned)should be an AC RC 26. However, mine has an RC 27 (15 lb. closed system). Is this a service replacement? Is it adequate for my operating (not judging) needs ? The rest of my seemingly original cooling system seems to be intact (Harrison tank #3016340 - 68A, and Harrison aluminum radiator) and in good condition, having passed a pressure test with no leaks.
  • Craig S.
    Extremely Frequent Poster
    • June 30, 1997
    • 2471

    #2
    Re: '68 L79 radiator cap question

    Dave - I have a 67 L79 and believe the RC26 is correct and the same for both, However, I have an RC27 on mine too (it also says made in Germany). It looks pretty much like the RC 26 and has the same aluminum rivet. I thought maybe I was the only one with this weird cap. It appears to be vintage in the sense it looks like the old caps.......curious.......Craig

    Comment

    • Dave F.
      Expired
      • December 1, 2003
      • 508

      #3
      Re: '68 L79 radiator cap question

      Mine also appears to be vintage, but doesn't say made in Germany, or anywhere else for that matter. On the upper half in large font it has "Never Open Hot". underneath that it has "check level in bottle" in smaller font. The rivet is copper. There are 2 arrows pointing to the outside on either side of the rivet. Underneath the left arrow is "AC", the right arrow is "RC 27". On the botton half along the edge it has "Align Arrow & Vent Tube". Just above that it has "15 LB Closed System. It is in good shape, but definitely has some age on it.

      Comment

      • Joe L.
        Beyond Control Poster
        • February 1, 1988
        • 43193

        #4
        Re: '68 L79 radiator cap question

        Dave----

        The RC-27 radiator cap, CURRENTLY known as GM #10409635, is a radiator cap of VERY wide application. It was first used for the 1966 model year for some non-GM applications and later came into very wide use for both GM and non-GM applications. Like most other GM radiator caps, this one has "evolved" with respect to the configuration of the cover. Early models are configured just like most other AC radiator caps of the period. The current examples have the stainless steel cover with small "ears".

        The only Corvette application for the RC-27 is 1991-96 Corvettes. The RC-27 is NOT designed for contact use with aluminum radiators or aluminum supply tanks. Although the 91-96 Corvettes did use an aluminum radiator, they also used a plastic surge tank which the radiator filler was a component of.

        An RC-26, which is still available, should be used for all 1963-72 Corvette applications with aluminum supply tanks.
        In Appreciation of John Hinckley

        Comment

        • Craig S.
          Extremely Frequent Poster
          • June 30, 1997
          • 2471

          #5
          Re: '68 L79 radiator cap question

          Thx Joe - guess I better check, I thought the vintage version RC27 in my 67 supply tank had an aluminum rivet vs copper, but maybe I am remembering wrong. It's up on a lift so I can't readily check, but I have to change out my old Harrison for a DeWitts repro anyway, and will make sure I use the restored RC26 I have....Craig

          Comment

          • Craig S.
            Extremely Frequent Poster
            • June 30, 1997
            • 2471

            #6
            Re: '68 L79 radiator cap question

            Thx Dave - I will have to check mine more carefully per Joe's post, maybe I am in error about the aluminum rivet but I was aware of the issue with the dissimilar metals and thought I had checked that point but may have missed it.....Craig

            Comment

            • Joe L.
              Beyond Control Poster
              • February 1, 1988
              • 43193

              #7
              Re: '68 L79 radiator cap question

              Craig------

              Whether or not the RC-27 has the "aluminum" rivet makes no difference. The rivet is not the primary difference between caps for aluminum contact and others. The RC-26 and "307" caps are otherwise insulated to prevent dissimilar metal corrosion.
              In Appreciation of John Hinckley

              Comment

              • Dave F.
                Expired
                • December 1, 2003
                • 508

                #8
                Re: '68 L79 radiator cap question

                Joe,

                Thanks for the information. Your knowledge never fails to amaze me. Also glad to know the RC 26's are still available. Looks like I'll have another part for my "garage art" collection - a nice, shiney stainless steel radiator cap

                Dave

                Comment

                • Dave F.
                  Expired
                  • December 1, 2003
                  • 508

                  #9
                  Re: '68 L79 radiator cap question

                  My cap must be relatively new, as I have no corrosion on the tank where the cap's ears come in contact with it. I definitely will replace it with an RC 26.
                  My garage art collection is growing at a faster pace than what I'd like

                  Comment

                  • Dick W.
                    Former NCRS Director Region IV
                    • June 30, 1985
                    • 10483

                    #10
                    Re: '68 L79 radiator cap question

                    Welcome to the real world of Corvettes. The "Garage Art" is a measure of how much fun you are having in the hobby:D:D No Art, No Fun! Lotsa Art, Lotsa Fun! Ask Doc McCagh. Has three garages full of art and also a barn full. No one has more fun than he does.
                    Dick Whittington

                    Comment

                    • Dave F.
                      Expired
                      • December 1, 2003
                      • 508

                      #11
                      Re: '68 L79 radiator cap question

                      Sounds like Doc is leading by example

                      Comment

                      • Dick W.
                        Former NCRS Director Region IV
                        • June 30, 1985
                        • 10483

                        #12
                        Re: '68 L79 radiator cap question

                        In that case, one H... of a leader.:D And a pretty good guy for a white headed old man:D
                        Dick Whittington

                        Comment

                        • Dave F.
                          Expired
                          • December 1, 2003
                          • 508

                          #13
                          Joe - one more question

                          Do you know how the new RC-26 caps are judged when compared to an original 1968 RC-26? Maybe a better way to ask this is if the new AC RC-26 caps are identical to the originals.

                          Comment

                          • Patrick H.
                            Beyond Control Poster
                            • December 1, 1989
                            • 11608

                            #14
                            Re: Joe - one more question

                            In one word, No, they are not the same as originals. They likely would suffer the same judging penalty as most current service replacement items. I suspect the new ones are also stainless steel, not zinc plated steel.

                            Having said that, consider that 1) I use a brand new RC-15 for driving and my original for judging; 2) you can have an original cap restored, and 3) if you're not in a hurry, a nice article will be coming out someday on the RC-26. You just have to wait for the RC-15 article first. We hope to show some information on all of this.

                            Patrick
                            Vice-Chairman (West), Michigan Chapter NCRS
                            71 "deer modified" coupe
                            72 5-Star Bowtie / Duntov coupe. https://www.flickr.com/photos/124695...57649252735124
                            2008 coupe
                            Available stickers: Engine suffix code, exhaust tips & mufflers, shocks, AIR diverter valve broadcast code.

                            Comment

                            • Dave F.
                              Expired
                              • December 1, 2003
                              • 508

                              #15
                              Re: Joe - one more question

                              Thanks Patrick. I can let you know if the new RC-26's are stainless steel tomorrow after I pick one up from my local AC parts dealer.

                              Comment

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