My carb is a 7040247. The date code below it is 0128. I thought that would be Jan 12, 1968. But the carb part number clearly shows it to be a 1970 Buick 455 Carb. So were carb date codes sometimes shown with year first? In that case it would be the 128th day of 1970, which fits carb number. If that is true, then that’s about a month before the build date of my car.
Ok. Next question. That date fits perfectly with my build date. Could this 7040247 have been used on my automatic 455 GS? I know it is generally thought Odd numbered last digits were manual trans cars and the 247 was a Rivera carb. My Car’s build date was June 19th 70. Very late production. Could Buick have used up the remaining 70 Model carbs? I was told the carb is original to the car.
I'd never say never. My '71 GS (350) is a late car & it seems Buick was using up distributors. IIRC the GS took a different one than a 4BBL Skylark (or maybe was 2BBL - Been a while since I researched it). Was a thread on here w/some confusion & mine was the same way & I'm 99% sure it's orig.
OK guys there is a problem here, and this is very important to understanding these codes. If you have a 7040247 carb, the 4th digit is the model year, therefore it would definitely be for a 1970 model year car. If it has a date code of 012 8, that would decode as the 12th day of 1968, which does not work as a date code for a 1970 model year car. Here is the answer. The date code has the Julian date first (day of the year), followed by the last digit of the year it was produced. (The year of production never precedes the Julian date.) The problem here is the number for the last year of production does not include the decade. This carb was most likely produced on the 12th day of 1978 and is a replacement carb. It probably also does not have the 2-letter application code after the part number. GM did a batch of replacement carbs for the 1971 Stage 1 motors, and at first glance the date code looks correct, but they were produced in 1980 not 1970. There are other ways to prove a carb was from a production model, but I will not go into them here. Duane
It’s hard to see the pic on my phone but that looks like a replacement carb. Guys, You have to be really careful when you buy carbs, as it is very easy to spend big money for a correct part numbered carb, only to find out it is a replacement. The carb on my 71 Stage 1 GSX is a replacement, but I knew that when I bought it, and it was priced accordingly. I think when we got it it was still plastic shrink wrapped onto the cardboard backing piece. I simply could not pass up a perfectly plated NOS carb for the price quoted. Duane PS, Someone should make this into a sticky, as there is some good info here for everyone. PSS, For those that want to look, the date code info for Rochester carbs is on page 14 of my book.
That depends on the model year and how common the parts are, because the parts were made and sent in batches. For the 70 model year Big Block Buicks were much more common, so the dates on those parts hug the body build date much closer. For the 71-72 model years Big Block Buicks were less common and some date codes tend to spread out a bit. Plus you need to deal with different plants etc. For more rare parts, like a Stage 1 carb or distributor, the dates will originally be close to the body built date. Then get further away until that batch gets used up. Then all of a sudden the dates get close to the body date again when the next batch of parts arrives. Lather, rinse, repeat. Now that is for the 1970 model year. For the 71-72 model years the Stage 1 cars were few and far between. Often the above two parts never got past the first batches. Duane
My memory of the main Qjet assembly lines (there were 3 I think in the 80's) at RPD was that they could certainly build a few hundred Qjets in a couple of hours. Model changeover seemed to eat a lot of time, with a small crew at the first station with papers figuring out and changing the stamping dies for the next batch, as well as hard parts being changed out from one model to the next at certain points on the line. There was a lot of attention given to that first stamping station, which was where the numbers were applied when the carbs entered main assembly. Imagine running a big batch of 1000's of Qjets with the wrong stamping? Again, memory withstanding, 2 out of the 3 lines were for main production, and the 3rd line was for service. Depending on the orders, they would run 3 shifts 7 days a week if need be.
My friend (ASE-certified Master Tech) and housemate brought home for me all of the GM 1967 Buick shop manual pages for full-size models which had the entire Rochester numbering scheme broken down & explained....a treasure trove of information. Those were the days when autos were all built in USA in on location by hand (Flint), and all of the maintenance info was illustrated & explained so that anybody with minimal hand tool experience could keep the vehicle running forever. I still bust out those very same pages from time-to-time when it comes to tinkering on the carb or other top-end pieces.
I think the service manuals are still available online or on CD-ROM, just grab a copy & print out the pages you need to bring to the garage.
^ This I have pics of the 64-65 Buick Misc Parts Manual and on the attached page the carb number matches my carb tag number. Mine is supposed to be the correct one for my year 300ci (64) 4bbl intake.
Newbie to Rochester carbs. So could an early GS455 have a 7040240 carb dated 2609? My GS body tag is 01B, second week in January? Or is there a 0010-0310 carb that I’m looking for?
