This info is from Cliff Ruggles, one of the best QuadraJet guys around. Here's Cliff's book: http://www.amazon.com/Rebuild-Modify-Rochester-Quadrajet-Carburetors/dp/1932494189 Here's Cliff's shop: http://www.cliffshighperformance.com/ FYI, Cliff also fields questions: Ask Cliff! Advice is free. Good advice comes from Cliff, but it's still free. Do you have a question about your Quadrajet? Have a carburetor problem you can't solve? Do you want advice for your specific Qjet application? Fill out this form and provide us with as much info as you can and we'll be able to reply ASAP with our suggestions and a quote. http://www.cliffshighperformance.com/quote.html HE EVEN HAS A QUADRAJET FORUM: http://www.cliffshighperformance.com/simplemachinesforum/ He's a hell of a nice guy. Y'all should check his site out, or hit him up for some parts or advice if you're having QuadraJet trouble - 5 minutes with Cliff might save you months of headaches! ~Jason
QUADRAJET CASTING NUMBER CHART HOW TO IDENTIFY A QUADRAJET AND DECIPHER THE CASTING NUMBERS Carburetor Designation/Identification CASTING NUMBERS Through the years of production, the manufacturer used numbers for carburetor identification. Very early Quadrajets had tags installed into a cast round area on the drivers side of the main body. Tag showing Quadrajet ID on an early Quadrajet In and after about 1968, stamped numbers were used for 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.
1966-1975 Rochester ID number breakdown for 7041240 from the illustrated example above. A 1971 Buick Federal Quadrajet 7041240 70 - Prefix for Rochester carburetors Decade Identifier 7041240 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 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
Transmission 7041240 1,3,5,7,9 - Odd numbers - manual transmission 0,2,4,6,8 - Even numbers - automatic transmission
I think that is the one that I looked at at Barnes & Noble a couple of weeks ago. I didn't buy it although I spent a half hour with my nose in it in a chair in the corner. I went back a week later to get it and someone had beat me to it. I'd say it's a must have for guys with Quadrajets. The chart on what fits what is a big help when one is digging through the batch of carbs on the back shelf to find the one that fits "that" engine correctly. I just ran into that and used the chart to figure out which carb I had was the right one for the 500 Cad I bought that had a way wrong carb on it.
Notes: 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 Plant codes identify which plant the carb was cast at. 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. WF Plant Code 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. 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. CARBURETOR DESIGNATION/IDENTIFICATION CASTING NUMBERS Although many castings are referred to by specific characteristics such as airflow capacity or choke type, Rochester actually gave each Quadrajet style different designations indicating body type and choke style. The first design series was designated 4M and can be found on all GM vehicles through 1974 and on GMC and Chevy trucks through 1977. When Rochester redesigned the Quadrajet in 1975, they referred to it in factory literature as the "Modified Quadrajet" or "Mod-Quad," and designated it M4M. When computer-operated electronic internal components were added around 1980, Rochester designated the Electronic Quadrajet the E4M. The last letter in the series designation generally indicates choke type. The letter "V" indicates an automatic choke where the thermostatic choke coil is fastened to the exhaust crossover on the intake manifold. Commonly referred to as a "divorced" choke, a small rod connects the coil to the mechanical linkage on the passenger side of the main body. The letter "C" indicates a carburetor-mounted automatic choke. In these instances, the thermostatic coil, which is mounted on the passenger side of the main body, uses heated vacuum and is easily recognizable by its large, black adjust ment disc. They are generally referred to as a "hot air" style. Most carburetors produced in and after about 1975 have the choke housing mounted on the carburetor. The thermo static coil is activated by hot air from the intake manifold exhaust crossover system via a heated tube. Later, electric chokes started showing up in certain applications to replace the hot-air-style chokes. The letter "E" indicates an electronic choke coil. They too, are recognizable by a large black disc, but they operate off of a 12-volt source as opposed to vacuum. And those Quadrajets without any letters following the 4M and M4M designation had a manual choke. The list below identifies the different types of Quadrajet designations that appear in AC Delco printed information. 4M: Quadrajet with manual choke 4MC: Quadrajet with carburetor-mounted automaticchoke 4MV: Quadrajet with divorced automatic choke 4ME: Quadrajet with carburetor-mounted electric choke M4MC: "Modified" Quadrajet with carburetor-mounted automatic choke M4ME: "Modified" Quadrajet with carburetor-mounted electric choke 4MEA: "Modified" Quadrajet with carburetor-mounted electric choke and "Altitude" calibration E4MC: "Electronic" Quadrajet with carburetor-mounted automatic choke E4ME: "Electronic" Quadrajet with carburetor-mounted electric choke For the complete story of the history and the function of the Quadrajet, and to learn how to rebuild, modify and restore any Qjet, purchase the book "How to build and modify Rochester Quadrajet Carburetors" by Cliff Ruggles from this website http://www.cliffshighperformance.com/
I have been recommending this book since BEFORE it hit the book stores. It is the most user-friendly carburetor book I have ever read; and one of the top 3 carburetor books period. It is useful even if you don't own a Q-Jet. The "coding" charts are correct probably 95 percent of the time (but that means they will get you in trouble 5 percent of the time)! Examples: 7028237 was original on a 1968 Cadillac. Odd last digit, but I can assure you it was not used with a manual transmission. 7028273 was originally a 1968 Pontiac RAII carb, but was carried over and used as original equipment on 1969 RAIII (4th digit 8). There are many other exceptions. Use the chart as a guide, but for absolute identification; check a guide BY PART NUMBER. Jon
I sent Cliff my qjet base plate to be rebuilt, it was cheaper to have them do it than buy the bushings and such my self. Had him send a rebuild kit when he shipped it back. Turn around was quick, and the kit was very complete. When I mistakenly drilled a passage too large, he mailed a couple of brass plugs so I could fix it. I had a question about which apt spring to use for my app (the kit has three), checked his forum and had my answer. Good guy to deal with.
Sorry - bumped on a weekend, with no one to see! LOL! BTTT for folks that will see this today. ~Jason
If you're a Poncho Head, you know Cliff. I met him at the Pontiac Southern Nationals in Dallas a few years back. He definately knows Q-jets and had plenty of good advice when I was racing my '72 Formula.
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