Decode your Rochester Carburetor

There are two codes to look for when decoding a Rochester carburetor, the model number and the date code. The model number will be a 7 or 8 digit number, depending on when it was produced. Carburetors built before 1976 use a 7 digit model number. Those produced after 1976 use an 8 digit model number. The date code is an alpha-numeric string.

Pre-1976

Let's look at some examples. A model number for a pre-1976 carburetor might look like 7028219, and the date code might look like DG1938. Each number has a meaning, so let's break these numbers into their component pieces.

First the model number: 70 - 2 - 8 - 2 - 1 - 9. This breaks down as follows:

70 - Prefix code
  70 will appear on all late 1960'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

Now the date code: DG - 193 - 8. This breaks down as follows:

DG - Customer code

1938 - Date Code
  193 - 193rd Day of the year
  8 - Year (1968)

Post-1976

A model number for a post-1976 carburetor might look like 17080243, and the date code might look like 2629CNO. Let's break these numbers into their component pieces.

First the model number: 170 - 8 - 0 - 2 - 4 - 3. This breaks down as follows:

170 - Prefix code

8 - Decade Produced
  5 - 1976-1979 (1705)
  8 - 1980's (1708)

0 - Year Produced (1980)

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

3 - Transmission
  Even numbers - Automatic Transmission
  Odd numbers - Manual Transmission

Now the date code: 262 - 9 - CNO. This breaks down as follows:

CNO - Customer code

2629 - Date Code
  262 - 262nd day of the year
  9 - Year