Through the years of production, the manufacturers of Quadrajet carburetors used numbers for carburetor identification. Very early Quadrajets had tags installed into a cast round area on the drivers side of the main body of the carburetor.
In and after about 1968, stamped numbers were used for Quadrajet Carburetor 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.
Identify a Quadrajet – Quadrajet Number Search
1966-1975 Rochester ID number breakdown
EXAMPLE – 7041240 – 1971 Buick Federal Quadrajet
70 – Prefix for Rochester carburetors
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
Not the model year
1966 or 1976 with a leading 1 in code
1967 or 1977 with a leading 1 in code
1968 or 1978 with a leading 1 in code
1969 or 1979 with a leading 1 in code
1970 or 1980 with a leading 1 in code
1971 or 1981 with a leading 1 in code
1972 or 1982 with a leading 1 in code
1973 or 1983 with a leading 1 in code
1974 or 1984 with a leading 1 in code
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 Emissions Specs
0 – Mono-jet
1 – Two-jets
2 – Quadrajet
3 – Mono-jet
4 – Two-jets
5 – Quadrajet
6 – Varijet
0, 1, 2
1,3,5,7,9 – Odd numbers – manual transmission
0,2,4,6,8 – Even numbers – automatic transmission
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 identify which plant the Quadrajet carb was cast at. These are 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. 68 and later they are on the casting as shown here “WF”.
Most Rochester built Q-jets used a four-number Julian Date code. The first three numbers are the Day of the Year the carburetor was built; the last number is the Year.
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.