To break the codes, you gotta know where to look. You'll find 'em on the driver side of the carb, on a vertical pad in the area of the secondaries. Early carbs used a circular metal disc stamped with the codes and attached to the same side, but further forward on the float bowl. Rochester-built carbs are denoted by the words "Rochester Quadrajet" cast into the driver side of the carb body. To break the codes, you gotta know where to look. You'll find 'em on the driver side of th From 1967 through 1972, the venerable Quadrajet carburetor was used on many Chevelles ordered with standard performance engines, and those applications will be the focus of this article. Quadrajets were manufactured by Rochester (a division of General Motors) and Carter carburetors. Outsourcing carburetor production allowed delivery to meet demand as the Q-jet was used on other Chevrolet models and virtually every other GM nameplate as well. With so many carbs in production for a myriad of applications, finding the right one for your Chevelle can be a challenge. There are a couple of locations containing the codes needed to identify your Quadrajet; both are located on the driver side of the carb body. Early Q-jets used a circular tag stamped with the codes found in a cavity in the side of the float bowl, while later carburetors used a stamping on the body of the carb. Breaking down the carb codes is fairly simple once you have some basic idea of how the system is setup. Information included in the stamped alpha-numeric codes are the model/application number (usually seven digits), and a date code. All Carter-built Q-jets have "Mfd by Carter" cast into the carb body, although the carb numbers (application codes) are the same as Rochester-built carbs. This is what the stamping will look like on a Rochester-built carb. This particular model came off a '70 Chevelle with an LS5 454/360-horse and a four-speed trans, non-CA emissions. This is what the stamping will look like on a Rochester-built carb. This particular model Carter-built carbs have their stampings in the same area, but differ slightly in configuration, even though the application codes are the same as Rochester-built carbs. This one came off a '71 Chevelle with a 270-horse 350 small-block backed by an automatic transmission. Carter-built carbs have their stampings in the same area, but differ slightly in configura The Carter-built carbs are also easily identified by the "MFD by Carter carburetor for GMC" cast in the same area on the driver side of the carb body. Carbs built by Carter also use the same rods, jets, hangers, etc. as the Rochester-built Q-jets. The Carter-built carbs are also easily identified by the "MFD by Carter carburetor for GMC Outin' The Code The stamped part number decodes as follows: Example: #70 4 0 2 0 5 EH 0260 70 = Prefix code. "70" will appear on all Q-jets through 1976 4 = Decade produced (ie: 2=1960's; 3=1960's with A.I.R.; 4=1970-1975) 0 - Year produced. 0=1970 2 = Model (ie: 2=Quadrajet (4 bbl) Federal standards; 5=Quadrajet (4 bbl) California standards) 1 - Division. 0, 1, and 2 all indicate Chevrolet. 9 - Transmission (ie: Even numbers=Automatic Trans; Odd numbers=Manual Trans) DG - Customer code (assigned for each application, matches carb code on build sheet) 0260 - Julian Date Code (026=26th day of the year; 0=year of production, 1970) 1 | 2 | » | View Full Article By Chuck Hansen Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!