How to Decode Rochester Quadrajet Carburetor Numbersby T.M. Samuels
Identification codes indicate the car or truck a carburetor was designed for and what transmission it was used with. ID numbers for a Rochester Quadrajet carburetor are found next to the throttle level. There should be a metal disc affixed to the carburetor for those in the 1965 to 1968 range, and the number was stamped into the unit without a metal disc on the later-year models. This is the number you need for decoding. It will be a string of numbers used for the identification of the carburetor, and below it will be letters and numbers used to tell the date of manufacture.
Check the first three digits. They reveal when the carburetor was made. A “702” is for the 1960s era, a “703” is for the 1960s with AIR -- an air injection reactor -- and “704” is for the years 1970 through 1975. If there is a “1705” or “1708” as the first four numbers, this still is the year of manufacture, even though it is more than three digits; “1705” is for 1976 to 1979, and “1708” is for the 1980s. AIR is an added unit that mixes fresh air into the engine. It was common in states with stricter emission controls, such as California.
The next digit identifies the exact production year. A 702 followed by an “8” is for 1968, and a 704 followed by a “5” is for 1975.
The next digit indicates the carburetor model. A “0” is for a federal standard one-barrel monojet; “1” is for a federal standard two-barrel, two-jet model; “2” is for a federal standard four-barrel quadrajet; “6” is for a federal standard two-barrel vari-jet; “3” is a California standard monojet; “4” is a California standard two-barrel two-jet; and “5” is a California standard four-barrel quadrajet.
The next-to-last number in the set is the division: “0,” “1” and “2” are for Chevrolet, “4” is for Buick, “5” is for Oldsmobile, and “6” or “7” is for Pontiac.
The last number is for the transmission. Odd numbers are for manual transmissions, and even numbers are for automatic transmissions.
The next set of letters and numbers indicates production. The letters are the production code. The first three numbers are for the day of the year the carburetor was made, and the last number is the year it was made. If there aren’t numbers, you have a Carter-produced carburetor, not a Rochester Quadrajet. For a complete example, "7028219 DG1938" translates as 1968 Federal standard Quadrajet from a Chevrolet with manual transmission. DG is the production code, and 1938 shows that it was manufactured the 193rd day of 1968.
- Zoran Zeremski/iStock/Getty Images