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emission equipment on a 75

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  • Jim Sherman
    #1

    emission equipment on a 75

    I have a 75 that "some" of the smog equipment was removed, brackets and all; and I have to pass emission testing(Ididn't do the removing). Now I'm trying to figure out what belongs back on. I have the charcoal canister, EGR valve, PCV valve, and all the temp controlled vac switches appear to be present. I also have a factory engineering drawings manual of all things. The confusion occurs on the air injection into the exhaust. The manual shows it going into the pipe below the heat riser, and the parts dealers show it going into the exhaust manifold at the exhaust valves. Who's right, or are both "proper" for emission inspection. Are the brackets for the air pump and vacuum operated heat riser particular to corvette or can I ask the junk yards for other models(I have noticed if you say corvette, the parts cost acquire a whole new meaning).

    TIA Jim
    Tags: None
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    • Joe L.
      Beyond Control Poster
      • February 1, 1988
      • 43193
      #2
      Re: emission equipment on a 75

      Jim----

      As far as I know, 1975 was the last year for the "traditional" A.I.R. injection tubes into the exhaust manifold for each cylinder, although there may also have been a connection below the exhaust manifold for "catalytic converter air". In 1976 the system was revised. Of course, if you have a late 75, who knows?

      As far as the brackets go, I believe that the A.I.R. pump bracket, GM #14007354, was a unique Corvette piece, although it may also have been used on some other Chevrolet models. The vacuum operated heat riser was used on other models---many of them. The former part number, GM #355915, has been discontinued and replaced with GM #5234825. However, this part carries a GM list price of $247.14.

      One other point: before you go investing in any replacement "smog" parts for your car, I'd check with a smog inspection station or your state's official smog agency. Find out what configuration that their books show as being "correct" and acceptable for your car. That's the system that you want to restore. In this case, their books define the "correctness" that matters and you will need to please them and not an NCRS/NCCB judge.
      In Appreciation of John Hinckley
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        • Joe L.
          Beyond Control Poster
          • February 1, 1988
          • 43193
          #3
          Re: emission equipment on a 75

          Jim----

          As far as I know, 1975 was the last year for the "traditional" A.I.R. injection tubes into the exhaust manifold for each cylinder, although there may also have been a connection below the exhaust manifold for "catalytic converter air". In 1976 the system was revised. Of course, if you have a late 75, who knows?

          As far as the brackets go, I believe that the A.I.R. pump bracket, GM #14007354, was a unique Corvette piece, although it may also have been used on some other Chevrolet models. The vacuum operated heat riser was used on other models---many of them. The former part number, GM #355915, has been discontinued and replaced with GM #5234825. However, this part carries a GM list price of $247.14.

          One other point: before you go investing in any replacement "smog" parts for your car, I'd check with a smog inspection station or your state's official smog agency. Find out what configuration that their books show as being "correct" and acceptable for your car. That's the system that you want to restore. In this case, their books define the "correctness" that matters and you will need to please them and not an NCRS/NCCB judge.
          In Appreciation of John Hinckley
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            • Bill Clupper
              #4
              Re: emission equipment on a 75

              I'm showing something slightly different for the bracketry, My 'Jan '75 parts book shows P/N 3923214 for the pump bracket. This P/N as Joe states does not show up in my '77 parts book with any pass car applications, but it is the same as all other 68-74 smallblock Corvette applications. Bill Hodel, who advertises in the Driveline can usually be a big help for smog stuff. I can't find a parts book reference that indicates the vacuum crossover valve was used in '75, so you may be in luck there. Check your judging manual & it should have more info on wether this was used.
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                • Bill Clupper
                  #5
                  Re: emission equipment on a 75

                  I'm showing something slightly different for the bracketry, My 'Jan '75 parts book shows P/N 3923214 for the pump bracket. This P/N as Joe states does not show up in my '77 parts book with any pass car applications, but it is the same as all other 68-74 smallblock Corvette applications. Bill Hodel, who advertises in the Driveline can usually be a big help for smog stuff. I can't find a parts book reference that indicates the vacuum crossover valve was used in '75, so you may be in luck there. Check your judging manual & it should have more info on wether this was used.
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                    • Joe L.
                      Beyond Control Poster
                      • February 1, 1988
                      • 43193
                      #6
                      Re: emission equipment on a 75

                      Bill----

                      The 3923214 A.I.R. pump bracket was a predecessor part number for the 14007354 bracket that I earlier mentioned. Both are nearly the same in configuration(except for the cast-in part number and a few other minor differences) and fully interchangeable. However, I thought that the 14007354 came into production use before 1975 inasmuch as the part number looks to be about a 1970 or 1971 issue. However, since I'm in the office at the moment, I don't have access to my references to check on this.
                      In Appreciation of John Hinckley
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                        • Joe L.
                          Beyond Control Poster
                          • February 1, 1988
                          • 43193
                          #7
                          Re: emission equipment on a 75

                          Bill----

                          The 3923214 A.I.R. pump bracket was a predecessor part number for the 14007354 bracket that I earlier mentioned. Both are nearly the same in configuration(except for the cast-in part number and a few other minor differences) and fully interchangeable. However, I thought that the 14007354 came into production use before 1975 inasmuch as the part number looks to be about a 1970 or 1971 issue. However, since I'm in the office at the moment, I don't have access to my references to check on this.
                          In Appreciation of John Hinckley
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                            • Bill Clupper
                              #8
                              Re: emission equipment on a 75

                              Joe, I checked the '214 part back to '68 with no pass interchange shown. I can't predict when the eight diget p/n would have come into production, although I thought it later than '75, at least in my division, although the changeover could have been staggered depending on when a division used up the old P/n allocation.
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                                • Bill Clupper
                                  #9
                                  Re: emission equipment on a 75

                                  Joe, I checked the '214 part back to '68 with no pass interchange shown. I can't predict when the eight diget p/n would have come into production, although I thought it later than '75, at least in my division, although the changeover could have been staggered depending on when a division used up the old P/n allocation.
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