Rochester Identification

You can usually find the carbs casting number and date code on the driverside of the carb stamped vertically.

A typical stamping;
7045213 YA
101 5

70 = Rochester products division#
45 = Production year, 4=1970's, 5=specific year, 1975
2 = Carb ID, 2=49 state Q-jet
1 = Division, 1=Chevrolet products
3 = Tranny ID*, Even number=Automatic, Odd number=manual
101 5 = Julian Date Code, Friday April 11 1975
YA = Engine assembly plant

# Carbs starting with 70xxxxx are pre-1976. Carbs starting with 170xxxxx are 1976 onwards.
An important note: Primary metering rods are different lengths for the two units, both rods are available from GM, and the new-part part numbers correspond with the carb. Rods whose p/n starts with a 7xyz are for the 70xxxxx carbs, and p/n 17xyz are for the 170xxxxx carbs.

* tranny ID is not cast in stone. This particular example was original equipment on an automatic equipped pickup truck.

Production Year

15 = 1960
19 = 1961
20 = 1962
2x = 1963-1969
3x = 1966-1967 A.I.R. equipped vehicles
4x = 1970-1975
5x = 1976-1979
8x = 1980-?

x=last digit of model year

Carb ID

0 = 49 state mono-jet
1 = 49 state 2bbl
2 = 49 state Q-jet
3 = California mono-jet
4 = California 2bbl
5 = California and high altitude Q-jet

Product Division

0,1,2 = Chevrolet
3 = Cadilllac
4 = Buick
5 = Oldsmobile
6,7 = Pontiac
8 = Non-GM, possibly Mercruiser Marine
9 = Special

Julian Date Code

From our above example code;
101 = Day of the year (1 thru 364/5)
5 = Last digit of manufacturing year. (0 thru 9). Utilize carb id for 60's, 70's, or 80's.
Some of those multiyear calanders with a look-up table have the Julian day of the year on them. If not, you'll just need to count out the days.

Engine Assembly Plant

YA = ?
FJY =?

Examples

Our example carb, 7045213
Is a Rochester carb, for the 1975 model year, 49 state (federal) Q-jet, Chevrolet Division with supposedly a manual transmission.
What it was originally installed on was a non-emmisions controlled 1975 3/4 ton Chevrolet Pickup truck with a 350 cubic inch engine and an AUTOMATIC transmission.

How about another? 17083222
Date Code 0183
Is a 1983 model year, 49 state Q-jet, Chevrolet division with an automatic tranny.
Manufactured on the 18th day of the year, in a year ending in 3. For, January 18 1983
Originally installed on a 1983 1/2 ton Chevy Pickup with a 305 and automatic tranny.

And one more for fun, 7043114
A 1973, 49 state 2bbl , Chevrolet division, with an automatic tranny.
Originally installed on a 1973 Nova w/350 and automatic tranny.

Remember to employ all safety precautions when working on any vehicle.
This information is only intended as an overview and may not include all the necessary information, data, or facts to complete the swap.
Remember, every vehicle is unique, and research for your particular vehicle is recomended.

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