Decoding a Quadrajet Carb

The following information covers how to decode your Rochester Carburator. The Quadrjet carbs are found in two forms, one produced prior to 1976, one produced after 1976. Examples of each form are as follows:

Produced before 1976

7028219
DG 1938

70 : Prefix code. "70" will appear on all late '60's Rochester Carburetors.
  2 : Decade produced.
      2 - 1960's
      3 - 1960's with A.I.R.
      4 - 1970-1975
    8 : Year produced. 8 = 1968
     2 : Model
         0 - Monojet (1 bbl) Federal standards
         1 - Two jet (2 bbl) Federal standards
         2 - Quadrajet (4 bbl) Federal standards
         3 - Monojet (1 bbl) California standards
         4 - Two jet (2 bbl) California standards
         5 - Quadrajet (4 bbl) California standards
         6 - VariJet (2 bbl) Fed
       1 : Division.
           0, 1, and 2 all indicate Chevrolet.
           4 - Buick
           5 - Olds
           6,7 - Pontiac
        9 : Transmission
            Even numbers - Automatic Transmission
            Odd numbers - Manual Transmission

DG 1938

DG : Customer code.
1938 : Date Code
       193 - 193rd Day of the year
          8 - Year

Produced 1976 or later

7080243
2629 CNO

170 : Prefix Code
   8 : Decade Produced
       5 - 1976-1979 (1705)
       8 - 1980's (1708)
    0 : Year Produced
     2 : Model
         0 - Monojet (1 bbl) Federal standards
         1 - Two jet (2 bbl) Federal standards
         2 - Quadrajet (4 bbl) Federal standards
         3 - Monojet (1 bbl) California standards
         4 - Two jet (2 bbl) California standards
         5 - Quadrajet (4 bbl) California standards
         6 - VariJet (2 bbl) Fed
      4 : Division.
          0, 1, and 2 all indicate Chevrolet.
          4 - Buick
          5 - Olds
          6,7 - Pontiac
          8 - Chev / Olds / GMC / Truck Non comp
       3 : Transmission
           Even numbers - Automatic Transmission
           Odd numbers - Manual Transmission
2629 CNO

2629 - Date Code
       262 - 262nd day of the year
          9 - Year
CNO - Customer Code
I've picked up 3 Quadrajet carbs: 1980 model ($5), 1973 Chev model ($5) and a 1975 Pontiac ($20) . I will use the 73 as it is a presmog carb and is better performing and has better idle adjustment than the smog carbs.

3 amigos

1980 GM carb, 1973 Chev Quadrajet and 1975 Pontiac model

I traded part of the frame off my 76 Camaro parts car for the 1975 carb thinking that it was a 1977 Pontiac Firebird carb but the serial number tells another story. We figured that it was worth about $20. I picked up the 73 and 80 Quads at the local wreckers. I wanted the Pontiac carb for the linkage as its the same as the Camaro linkage that I am using now and the 73 for the performance or so I thought.

The serial numbers are stamped on the driver's side of the secondaries. Here's the numbers and what I've decoded:

SERIAL NUMBER

7043208
  43 - indicates 1973
    2 - Quadrajet 4 bbl
     0 - Indicates Chevrolet
      8 - Indicates automatic transmission

7045268
  45 - indicates 1975
    2 - Quadrajet 4 bbl
     6 - indicates Pontiac
      8 - indicates automatic transmission

17080282
  80 - indicates 1980
    2 - Quadrajet 4 bbl
     8 - 1980-85 Chev / Olds / GMC / Truck Non comp
      2 - indicates automatic transmsion

I will be rebuilding the 1973 which comes from a 1973 Chevy pickup. I am quite familar with it as I had a 1972 Vette with a Quadrajet on it.

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Copyright April 2011 Eugene Blanchard