Hey guys, does anyone have a definitive list of the Buick 455 carbs that are the 800 CFM? I am looking into the possibility of buying a reman carb, and putting richer rods and jets into it. Thanks!
71 - 74 are the best ones to use... Going up into the 75, 76 carbs, you have lots more smogger stuff to deal with...but they can be made to work well.
Thanks Adam! That's a drag about the 75's and up. I really wanted to go with the 75 or newer - ONLY because they have an integral choke (easy to convert to elec choke)! Thanks again for your quick reply!
FloydsBuick on the board here used the integral chokes on his early carbs, as they are adaptable to the early carb bodies. Might want to PM him for more info on that.. I used a 76 carb on my car a couple years ago...worked well. I had a hard tiem adjusting the electric choke though.
71-74, only 455 carbs, the 350 carbs were 750's. Here's a partial list: 7041242, 7041243, 7041540, 7042240, 7042242, 7042243, 7042942, 7043240, 7043242, 7043243, 7044141, 7044240, 7044242. Happy Hunting! :TU: Also here is a helpful picture that has been posted before. It shows the bump in the outer venturi, and identifies an 800 CFM Q-jet
One thing that this picture doesn't show is that the 3rd venturi in an 800 cfm Qjet is noticeably smaller (less restriction) than the larger 3rd venturi in a 750 version. Side by side, they are easy to tell apart.
Bob, Just the opposite. The 800 3rd venturi is 1 7/32", the 750 has 1 3/32". That's a 1/8" difference. That bump is an internal passage, the larger venturi would uncover it, so theres a bump. The 800's are jetted richer in the primarys than the 750.
Larry, yes you are correct. Smaller "bump" = larger venturi = 800 cfm. Only Buicks 71-73 and Pontiac in 73 used the 800 cfm version. Interesting that this flow rating was only attainable with the secondary air valve opened to 90. To the best of my knowledge, no stock production quadrajet ever came with a 90 setting because best distribution was attained at angles less than that. I don't know if GM ever put an advertised rating on their Qjets, but there is a noticeable primary flow difference in the large primary venturi versions vs the smaller ones. When RPD sold the tooling to make QJets, I'm not sure what size carbs the subsequent owners of the tooling produced. From a casting standpoint, I can't believe Carter, Weber, or Edelbrock (I'm not sure who actually owns the tooling) would bother to go to the expense of making more than a few different versions (one basic casting) and they all look like OEM Chev castings to me. I see new, 800 cfm QJets advertised in Summit, etc, but they can play games with the flow capacity ratings... I have purchased jets and rods from Summit and the quality of whoever is making them now is no where as good as it was when RPD made them. Like I said in another post, I worked at Rochester Products from 82-87, and the manufacturing process of a Quadrajet was a lot more complicated than most people realize. One project that I was involved in on the Quadrajet was to determine the feasibility of plating the secondary metering rods after bending the hanger tip. The traditional method of plating before bending would result in a lot of rejected rods because the plating would crack. There were a lot of scrap rods being produced! The problem with plating after bending was the thickness of the plating on the tip could allow the metering rod to fall out of specifications from a metering standpoint. Plating before bending enabled the variations in the plating thickness on the tip to be accounted for. The plating process over the years got better, and I was able to prove that it could be done, but then the powers that were pulled the plug on the whole project because by that time the writing was on the wall for carburetors. :Smarty:
