uzzled: I've discovered thru the carb number ID on my quadrajet, which is now on my '71 Riv GS that the carb. was originally on a 350CID 1971 Buick of unknown model. Should I seek out the correct carb. for my 455 ? Will it make a difference performance wise and are there any engine concerns running a carb. that was intended for a 350 engine? The number I have is 7041544. The number I should have is a 7041540, or 7041542. It runs OK and all, but I know the jetting and other specs must have an influence...but how much ? and so forth....please advise ? Thanks. I await your experienced knowledge........... 3 days later.....my post note/edit to this question......Well, I bought a correct number carb. off of E-bay and plan to rebuild that one and install it. That way the above is null and void. Then I can even burn more rubber...and know I have the correct orginal carb.
That is the same carb that was on my 70 GS when I bought it. It is a 750 CFM unit meant for a 350 Buick. Mine was jetted by the previous owner, and the car ran OK. That 71 engine came with an 800 CFM Q-jet. Buick put the 800 on all their big blocks starting in 71. The biggest difference in the big block carbs is the idle system. The big block carbs have extra passages that allow more air during idle. It's called a fixed idle air bypass. How does the car idle? Do you find that the idle needs to be a little high in nuetral to idle well in gear? Is the motor stock? I have a mild performance cam and headers. I could never get the car to idle right and my exhaust crossover is blocked off so I don't use a choke. I had alot of trouble when the motor was cold. I would have to drive it with 2 feet until it warmed up thoroughly. What I did was find an 800 CFM big block carb (7042240-1972 455), and sent it off to John Osborne. Now, without a choke, even in cold weather, I pump it 2-3 times, start it, and keep it running for about a minute, and it will idle all by itself. Noticed a little more power too. You can get yourself any 800 CFM carb from 71-74 and that will work for you. I've posted the carb #'s a few times on this BB. If you do a search on 800 CFM carbs it should come up. Hope that helps.
