Decoding Rochester Quadrajet Carburetor Numbers

Quadrajet Carb Number Basics

Detail of carburetor number and date code on 1976 Chevrolet Quadrajet

Rochester carb numbers consist of a carburetor number and sometimes an assembly line code and a build date code.

For example, 17056211 2615 ADF is a carb number (7029202) followed by a date code (2615) and a line code (ADF). The last digit of the date code is the last digit of the year the carburetor was built. The first three digits are the Julian date - the day number in that year: January 1 is day 001; Dec 31 is either day 365 or day 366 (in leap years).

  • 17056211: 1976 Chevrolet 350 manual transmission
  • 2615: Day 261 of 1975, so Thursday, September 18, 1975
  • ADF: assembly line code

More about finding Rochester carburetor numbers

1965-1969 without AIR (Air Injection Reactor) emission controls

702YXXX eg. 7026202

  • 702: All numbers in this period start with this except AIR
  • Y: The last digit of the year.
    7026XXX is a 1966 carburetor number
  • XXX: The carb number in this year. Usually tells you about the engine model. See Details, below.
    7026202 is a Chevrolet 327 automatic trans QJet

1966-1967 with AIR (Air Injection Reactor) emission controls

703YXXX eg. 7037202

  • 703: All AIR carbs start with 703. 1966-1967 only, generally sold in California.
  • Y: The last digit of the year.
    7036XXX is a 1966 carburetor number
  • XXX: The carb number in this year. Usually tells you about the engine model. See Details, below.
    7036202 is a Chevrolet 327 automatic trans QJet with AIR

1970-1975

704YXXX eg. 7040202

  • 704: All 1970 to 1975 carbs start with 702.
  • Y: The last digit of the year.
    7040XXX is a 1970 carb number.
  • XXX: The carb number in this year. Usually tells you about the engine model. See Details, below.
    7040202 is a Chevrolet 350 automatic trans QJet

1976-1979

1705YXXX eg. 17056202

  • 1705: All 1976 to 1979 carbs start with 1705.
  • Y: The last digit of the year.
    17056XXX is a 1976 carb number.
  • XXX: The carb number in this year. Usually tells you about the engine model. See Details, below.
    17056202 is a Chevrolet 350 automatic trans QJet

1980-1989

1708YXXX eg. 17084204

  • 1708: All 1980 to 1989 carbs start with 1708.
  • Y: The last digit of the year.
    17084XXX is a 1984 carb number.
  • XXX: The carb number in this year. Usually tells you about the engine model. See Details, below.
    17084204 is a Chevrolet 305 automatic trans QJet

Details: Decoding the Last Three Digits

The last 3 digits of the carburetor number tell about the engine type, whether the transmission is automatic or standard, and more.

For example, 7041200 L0 FA is a carb number (7041200) followed by a date code (L0) and a line code (FA). In this case, this is a Carter-built Quadrajet and a Carter style date code is used. Later Carter-built QJets use Rochester type date codes (as in the example at the top of this page).

  • 7041200: 1971 Chevrolet 454 automatic transmission
  • L0: L is the 11th letter, not counting I, so this is November. 0 is the year, 1970. A day number is not given in 2 character Carter date codes.
  • FA: the assembly line code.

Federal vs California

  • 2XX: Federal emissions QJet numbers mostly end in 2XX, for example 7040202 is a 1970 Chevy 350, Federal emissions.
  • 5XX: California emissions usually end in 5XX, for example 7040502 is a 1970 Chevy 350, California emissions. Otherwise, the numbers are similar.

There are some exceptions, especially with Buicks and Oldsmobiles (see below). 1980s Chrysler carbs were in the 4XX series.

Automatic and Standard Transmissions

  • Even: These are usually automatic transmissions. 7040202 is a 1970 Chevy 350 automatic, Federal emissions.
  • Odd: Usually manual transmissions. 7040203 is a 1970 Chevy 350 manual transmission, Federal emissions.

There are exceptions, especially with trucks where this rule is mostly ignored. For example, 17058213 is 1978 Chevy 350 truck with either manual or automatic transmission. 17058212 is Chevy 454 truck with either manual or automatic.

Engine manufacturer (last 2 digits)

  • 200-220s, 290S: Chevrolet engines are in the 200s to the 220s.
    17085222 is a 1985 Chevrolet truck carb.
  • 230s: Cadillac engine.
    17056231 is a 1976 Cadillac 500.
  • 240s: Buick engine. (Early models were in the 140s)
    7044244 is a 1974 Buick 350.
  • 250s: Oldsmobile engine. (Early models were in the 150s)
    17057253 is a 1977 Oldsmobile 403.
  • 260-270s: Pontiac engines. 270 series numbers are usually higher performance engines.
    7029262 is a big-car Pontiac, 7029270 is a Ram-Air engine.
  • 280s: Mostly special cases. Often marine engines or Canadian and other export production.
    17084284 is a Canadian 1984 Chevy 305 M4ME carb (US used E4ME computer controlled carbs)

There are some exceptions, especially with early models which were occasionally in the corresponding 100 series, such as Oldsmobile, eg. 7027156 (1967 Olds) and Buick, eg 7027146 (1967 Buick). There are other exceptions, but the engine manufacturer rules for the second-to-last digit usually apply.

Big Block vs small block

  • Big block Chevy: These often end in 200 or 201 when a big block (396, 402, 454) was offered.
    7040201 is a 1970 Chevy big block with a manual transmission, but 7040203 is small block
  • Buicks: 240 is the big engine (430, 455), 244 is the small engine (350). Riviera, Stage 1 or 2 models and special models in general have higher numbers, like 247 (even when automatics at times).
    7040240 is a 1970 Buick 455, 7040244 is a Buick 350, 7040247 is a Riviera 455 (automatic)
  • Oldsmobile: Opposite rules - 250 is the small engine (eg. 350), 251 is the big engine (eg. 455). Toronados, W and other special models have higher numbers.
    7040250 is a 1970 Olds 350, 7040251 is a 1970 Olds 455, 7040252 is a 1970 Olds 455 Toronado, 7040258 is a 1970 Olds W-30 automatic.
  • Pontiac: Can't distinguish big and small engines this way, but high performance is generally in the 270s, base performance in the 260s.
    7040264 is 1970 Pontiac 400, 7040270 is a 1970 Pontiac Ram Air 400 or 455

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