Date coding explained

[Absinth]

7041240
70 - Prefix for Rochester carburetors


Decade Identifier
7041240

2 - 1960's
3 - 1960's
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


Division7041240

0, 1, 2, Chevrolet
3, Cadillac
4, Buick
5, Oldsmobile
6, 7Pontiac


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.
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.

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.

Information from,
"Rochester carbs by cliff ruggles"