Correct Finish for '66 Exhaust Clamps - NCRS Discussion Boards

Correct Finish for '66 Exhaust Clamps

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  • Greg T.
    Expired
    • January 1, 2004
    • 136

    Correct Finish for '66 Exhaust Clamps

    Any one know the correct finish for exhaust clamps? I have natural U bolt and base with zinc flange bolts.
    Attached Files
  • Joe L.
    Beyond Control Poster
    • February 1, 1988
    • 43211

    #2
    Re: Correct Finish for '66 Exhaust Clamps

    Originally posted by Greg Thompson (41250)
    Any one know the correct finish for exhaust clamps? I have natural U bolt and base with zinc flange bolts.
    Greg------


    The u-bolt and clamp were NATURAL finish on original clamps (RUST almost immediately).

    The nut was usually a standard, NATURAL finish hex nut. It's POSSIBLE that the crossmember position did use a flanged nut but I don't think that a serrated-type, as pictured, was used.

    By the way, the u-bolt and clamp pictured APPEAR to be stainless steel. While I HIGHLY recommend the use of stainless steel exhaust clamps and other components, parts of said material were not originally used.
    In Appreciation of John Hinckley

    Comment

    • Greg T.
      Expired
      • January 1, 2004
      • 136

      #3
      Re: Correct Finish for '66 Exhaust Clamps

      Thanks Joe, they're plain steel. The 66 JG calls out "collared hex nuts" for the crossmember clamps.

      Comment

      • Joe L.
        Beyond Control Poster
        • February 1, 1988
        • 43211

        #4
        Re: Correct Finish for '66 Exhaust Clamps

        Originally posted by Greg Thompson (41250)
        Thanks Joe, they're plain steel. The 66 JG calls out "collared hex nuts" for the crossmember clamps.

        Greg------



        Well, that just goes to show how close carbon steel and stainless steel are in APPEARANCE.

        Of course, a judge with a magnet can tell the difference. However, I TOTALLY disagree with the use of a magnet during judging. NCRS standards are based upon how close any part is in APPEARANCE COMPARED TO ORIGINAL PARTS. The use of a magnet does not represent an APPEARANCE test; it represents a quasi-analytical methodology.
        In Appreciation of John Hinckley

        Comment

        • Scott S.
          Extremely Frequent Poster
          • September 11, 2009
          • 1961

          #5
          Re: Correct Finish for '66 Exhaust Clamps

          Originally posted by Joe Lucia (12484)
          Greg------


          The u-bolt and clamp were NATURAL finish on original clamps (RUST almost immediately).
          Joe,

          Were the original clamps for the stainless steel exhaust tips also natural steel finish?

          I have one NOS example in the original black and yellow GM paper envelope, the clamp body, U-bolt, split lock washers and regular hex nuts all look very dark gray with age. I also have a pair of exhaust tip clamps that appear to be NOS but did not come with GM packaging, and look like they're zinc plated.

          All three of them have "GM 3754883" stamped into them, along with "2" inside a circle, and the Patent number.

          Comment

          • Michael H.
            Expired
            • January 29, 2008
            • 7477

            #6
            Re: Correct Finish for '66 Exhaust Clamps

            Originally posted by Scott Smith (50839)
            Joe,

            Were the original clamps for the stainless steel exhaust tips also natural steel finish?

            I have one NOS example in the original black and yellow GM paper envelope, the clamp body, U-bolt, split lock washers and regular hex nuts all look very dark gray with age. I also have a pair of exhaust tip clamps that appear to be NOS but did not come with GM packaging, and look like they're zinc plated.

            All three of them have "GM 3754883" stamped into them, along with "2" inside a circle, and the Patent number.
            Scott,

            I agree on the grey colored plating/coating on NOS 3754883 tail pipe clamps. Here's another NOS set. The nuts appear to have the coating too.
            Last edited by Michael H.; November 21, 2011, 05:13 PM.

            Comment

            • Joe L.
              Beyond Control Poster
              • February 1, 1988
              • 43211

              #7
              Re: Correct Finish for '66 Exhaust Clamps

              Originally posted by Scott Smith (50839)
              Joe,

              Were the original clamps for the stainless steel exhaust tips also natural steel finish?

              I have one NOS example in the original black and yellow GM paper envelope, the clamp body, U-bolt, split lock washers and regular hex nuts all look very dark gray with age. I also have a pair of exhaust tip clamps that appear to be NOS but did not come with GM packaging, and look like they're zinc plated.

              All three of them have "GM 3754883" stamped into them, along with "2" inside a circle, and the Patent number.

              Scott------

              In PRODUCTION the exhaust clamps were supplied as each of their individual separate parts and not as a unit consisting of u-bolt, clamp, nuts, and washers. In SERVICE the clamps were supplied as a unit consisting of the above-referenced components. Sometimes, the U-bolt component was also available separately. In this case, though, the GM #3791371 U-bolt was never available separately in SERVICE.

              It's possible that the clamp UNIT supplied under GM #3754883 consisted of the same components used in PRODUCTION. However, if that were the case, I would not expect the clamp to be stamped 3754883. As far as I know, the originals were not so-stamped.

              One other thing: in the photo that Michael has posted of a GM #3754883, the nuts and lock washers appear to be phosphate-finished the same as the U-bolt and clamp. The nuts and washers used in PRODUCTION, GM #102634 and GM #103320, respectively, were of PLAIN finish.

              Also, the exhaust tip clamps originally used on my 1969, although of different part numbered U-bolt and clamp than the 66 application, were of natural finish and were completely rusted soon after I bought the car new.
              In Appreciation of John Hinckley

              Comment

              • Scott S.
                Extremely Frequent Poster
                • September 11, 2009
                • 1961

                #8
                Re: Correct Finish for '66 Exhaust Clamps

                Mike and Joe,

                Here are some pictures of the examples I referenced above. Note that the "GM 3754883" part number is upside down on one example, and the darker example has a "flat" face while the (zinc plated?) examples have the raised horizontal "bar".

                Thoughts or comments appreciated as always!
                Attached Files

                Comment

                • Ronald L.
                  Extremely Frequent Poster
                  • October 18, 2009
                  • 3248

                  #9
                  Re: Correct Finish for '66 Exhaust Clamps

                  Service parts could have been processed differently to give them some shelf life and not end up as a ball of rust sitting on the shelf.

                  Comment

                  • Lance H.
                    Expired
                    • December 1, 2004
                    • 48

                    #10
                    Re: Correct Finish for '66 Exhaust Clamps

                    Having worked on midyears in dealers when they were new I can tell you the cars arrived with exhaust clamps that varied somewhat, although all of the "guilotine" or "spade" type, with a light zinc plating that rusted readily. Some had a part number embossed, some a patent number, some just the size, some with nothing. Some had nuts with a shoulder, some with nuts without a shoulder. All had lock washers.

                    Here is a pic of a NOS 2 1/2". The flip side has "2 1/2" on it. My 1966 427-425 32,000-mile time-warp survivor has its original clamps on its off-road exhaust and both front and rears are identical to this, other than the rears being 2".

                    Lance Hill
                    Attached Files

                    Comment

                    • Scott S.
                      Extremely Frequent Poster
                      • September 11, 2009
                      • 1961

                      #11
                      Re: Correct Finish for '66 Exhaust Clamps

                      Originally posted by Lance Hill (43041)
                      Having worked on midyears in dealers when they were new I can tell you the cars arrived with exhaust clamps that varied somewhat, although all of the "guilotine" or "spade" type, with a light zinc plating that rusted readily. Some had a part number embossed, some a patent number, some just the size, some with nothing. Some had nuts with a shoulder, some with nuts without a shoulder. All had lock washers.

                      Here is a pic of a NOS 2 1/2". The flip side has "2 1/2" on it. My 1966 427-425 32,000-mile time-warp survivor has its original clamps on its off-road exhaust and both front and rears are identical to this, other than the rears being 2".

                      Lance Hill
                      Lance,

                      Thanks for posting, it's always good to hear from someone with personal experience about these kinds of things when they were new. Is the "spade" type exhaust clamp different than a "Guillotine" clamp, or just another word for the same type of clamp?

                      Do you recall whether all of the clamps (2" and 2-1/2") had the raised horizontal "bar" across the bottom like the one in your picture, or did that also vary from car to car?

                      Comment

                      • Gene M.
                        Extremely Frequent Poster
                        • April 1, 1985
                        • 4232

                        #12
                        Re: Correct Finish for '66 Exhaust Clamps

                        Originally posted by Joe Lucia (12484)
                        Greg------



                        Well, that just goes to show how close carbon steel and stainless steel are in APPEARANCE.

                        Of course, a judge with a magnet can tell the difference. However, I TOTALLY disagree with the use of a magnet during judging. NCRS standards are based upon how close any part is in APPEARANCE COMPARED TO ORIGINAL PARTS. The use of a magnet does not represent an APPEARANCE test; it represents a quasi-analytical methodology.
                        Joe you are SO RIGHT. I agree 100%, no aids should be tolerated by the owners. As an owner one can demand that no "instrument" be put in contact with his car. I just wonder how far an owner can take this beyond a chapter meet. The last I knew appearance is via one's eyes....

                        Comment

                        • Joe L.
                          Beyond Control Poster
                          • February 1, 1988
                          • 43211

                          #13
                          Re: Correct Finish for '66 Exhaust Clamps

                          Originally posted by Lance Hill (43041)
                          Having worked on midyears in dealers when they were new I can tell you the cars arrived with exhaust clamps that varied somewhat, although all of the "guilotine" or "spade" type, with a light zinc plating that rusted readily. Some had a part number embossed, some a patent number, some just the size, some with nothing. Some had nuts with a shoulder, some with nuts without a shoulder. All had lock washers.

                          Here is a pic of a NOS 2 1/2". The flip side has "2 1/2" on it. My 1966 427-425 32,000-mile time-warp survivor has its original clamps on its off-road exhaust and both front and rears are identical to this, other than the rears being 2".

                          Lance Hill
                          Lance------


                          I'm not surprised, at all, that there were slight variations in the configurations of these clamps. At the time, GM was using these clamps by the millions. I'm sure there were several different suppliers. While I'm sure they all met the basic GM specifications for the clamps, there could easily have been slight configurational differences in the product of each that did not contravene the basic specifications.
                          In Appreciation of John Hinckley

                          Comment

                          • Lance H.
                            Expired
                            • December 1, 2004
                            • 48

                            #14
                            Re: Correct Finish for '66 Exhaust Clamps

                            Originally posted by Scott Smith (50839)
                            Lance,

                            Thanks for posting, it's always good to hear from someone with personal experience about these kinds of things when they were new. Is the "spade" type exhaust clamp different than a "Guillotine" clamp, or just another word for the same type of clamp?

                            Do you recall whether all of the clamps (2" and 2-1/2") had the raised horizontal "bar" across the bottom like the one in your picture, or did that also vary from car to car?
                            Hi Scott,

                            Yeah, two different names for the same style of clamp. All of them did have the raised bar across the bridge.

                            Attached are pics of another clamp used at the time, and that I remember clearly, although in all honesty can't remember if they were on 1960s Corvettes, or maybe (only?) on Chevelles, Camaros or other GM vehicles. They were much less common than the guillotine type.

                            By the way, I need another of the guillotine type w/raised bar in 2 1/2 to go with the single I have, if anybody has one or knows where I can scare one up.

                            Lance
                            Attached Files

                            Comment

                            • Joe L.
                              Beyond Control Poster
                              • February 1, 1988
                              • 43211

                              #15
                              Re: Correct Finish for '66 Exhaust Clamps

                              Originally posted by Lance Hill (43041)
                              Hi Scott,

                              Yeah, two different names for the same style of clamp. All of them did have the raised bar across the bridge.

                              Attached are pics of another clamp used at the time, and that I remember clearly, although in all honesty can't remember if they were on 1960s Corvettes, or maybe (only?) on Chevelles, Camaros or other GM vehicles. They were much less common than the guillotine type.

                              By the way, I need another of the guillotine type w/raised bar in 2 1/2 to go with the single I have, if anybody has one or knows where I can scare one up.

                              Lance
                              Lance------


                              Is there a readable GM part number on the packages?
                              In Appreciation of John Hinckley

                              Comment

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