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technical articles

Carburetor Designation/Identification

CASTING NUMBERS
Through the years of production, the manufacturer used numbers for carburetor identification. Very early Quadrajets had tags installed into a cast round area on the drivers side of the main body.
Tag showing Quadrajet ID number on an early Q-jet
Tag showing Quadrajet ID on an early Quadrajet

In and after about 1968, stamped numbers were used for identification. The large flat area on the main body just above the secondary throttle shaft has a series of numbers stamped into the casting. In most cases these numbers can be used to identify the year and application the carburetor was originally used on.
Carburetor Numbering Chart for a Quadrajet carb

1966-1975 Rochester ID number breakdown for
7041240 from the illustrated example above.
A 1971 Buick Federal Quadrajet
 
7041240    
70 - Prefix for Rochester carburetors
 
Decade Identifier    
7041240
2 - 1960's
3 - 1960's with A.I.R (California Only Smog equipment)
4 - 1970 to 1975
5 - 1976 to 1982
 
Year of Manufacture    
7041240 Not the model year
6 1966 or 1976 with a leading 1 in code
7 1967 or 1977 with a leading 1 in code
8 1968 or 1978 with a leading 1 in code
9 1969 or 1979 with a leading 1 in code
0 1970 or 1980 with a leading 1 in code
1 1971 or 1981 with a leading 1 in code
2 1972 or 1982 with a leading 1 in code
3 1973 or 1983 with a leading 1 in code
4 1974 or 1984 with a leading 1 in code
5 1975 or 1985 with a leading 1 in code
After 1975 Carb will have an 8 digit code starting with 1 - i.e; 1704..
 
Model Federal / California    
7041240    
0 - Mono-jet 1-bbl Federal Standards
1 - Two-jets 2-bbl Federal Standards
2 - Quadrajet 4-bbl Federal Standards
3 - Mono-jet 1-bbl California Standards
4 - Two-jets 2-bbl California Standards
5 - Quadrajet 4-bbl California Standards
6 - Varijet 2-bbl Federal Standards
 
Division
7041240
0, 1, 2 Chevrolet
3 Cadillac
4 Buick
5 Oldsmobile
6, 7 Pontiac
 
Transmission    
7041240  
1,3,5,7,9 - Odd numbers - manual transmission
0,2,4,6,8 - Even numbers - automatic transmission

Notes:
Carburetors produced until 1969 begin with a 702 followed by four additional numbers. Some Carter-produced models lack the "70."

The 5th number is either a "1" or "2," indicating federal (49 state) emissions, or a "4" or "5" denoting California emissions.

The 6th number indicates the division application. "8" is Checker and Marine. The last number indicates the exact application. For the most part, even numbers were used on automatic transmissions, and odd numbers on manual transmissions, but there were numerous exceptions.

For carburetors produced from 1970 to 1974, the first three numbers are "704" followed by the same sequence of numbers as the "702" series of carburetors. (Some 704 carburetors were produced early in the 1975 model run; later units start with "1705.")

1975 and later Carbs
Staring in the 1975 model year, a "1" was placed in front of the "7" followed by "705." The "1705" series of carburetors would run until 1979. Beginning in 1980, the first four numbers were changed to "1708," and this number series would continue until the last carburetors were produced in the late 1980s.

PLANT CODES
Plant codes
identify which plant the carb was cast at. Usually two or three letters and the date that the carburetor was produced. They may be located with the stamped numbers. On 1966 built Carbs they are on the round tag.Quadrajet showing the Stamped 1968 and up date and plant code.
WF Plant Code

DATE CODE
Most Rochester built Q-jets used a four-number Julian date. The first three numbers are the day of the year the carburetor was built; the last number is the year.
For example:

Carburetor number 17058201 followed by a Julian date of 1238 would have been built the 123rd day of 1978.

One must keep in mind when dating carburetors that the year of production may not always be the same year as indicated by the carburetor number. Quite a few service replacement carburetors were produced. It is quite common to find much later production dates then what is indicated by the carburetor number. In addition, Carter carburetors produced in the late 1960's may have been used in a different model year then the number shown on the carburetor. This was most common in the 1968-1969 models. Rochester was not able to keep up with production.

Many Carter Quadrajets produced in these years may have been carried over to the next model year. This information is most important to restorers. It could be correct to have a fully restored 1969 Pontiac GTO using a Carter Carburetor produced in 1968.

It is important to note that there are quite a few exceptions to the basic numbering we have described above. One should always give a carburetor a close visual inspection. With rare high-performance carburetors bringing in excess of $2,000.00, there are always those who are going to re-stamp low-performance units.

For the complete story of the history and the function of the Quadrajet, and to learn how to rebuild, modify and restore any Qjet, purchase the book
"How to build and modify Rochester Quadrajet Carburetors"
by Cliff Ruggles from this website

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