So last year I bought a 71 Skylark with a low mileage, bone stock 76 455 in it. It sat for several years before I got it, but it runs and drives alright I guess. I say alright because the carb seems to have some issues. First the idle is very weird, sometimes it'll idle super high, other times super low and rough. I thought I found the problem with a leaking manifold gasket, but changing that seems to have made it worse. It is also a serious dog. I thought even a bone stock smog motor would still go okay in a lightweight Skylark, but it's such a slug. Compression is good, engine seems healthy and cylinders still have cross hatching in them even (had to pull the oil pan), heck it's even getting 17mpgs, but I'm quite suspect of the carb cause it seems like the secondaries don't even open or if they do it's barely at all. So, I'm likely going to send it off to get rebuilt probably at quadrajetpower.com, but I wonder if the '76 455 Quadrajet is worth getting built or if I should find an earlier or different core? Eventually I plan on building the engine up but for now it's bone stock and I'd just like it to run right. I've always been a fan of the QJ on a Buick, when they're working right. Suggestions?
Hi Andy. The 76 Buick 455 Quadrajet is a very good carb core to build from. It is 800 cfm capable and has adjustable part throttle system. I use the cores to build and modify when my customers want an electric choke. They are a "hot air" choke system originally. It will need a few tweaks and tricks, but it can perform great for you.
There are several guys here on V8 who can build and calibrate your Q-jet for you. Ken at Everyday Performance, http://www.v8buick.com/forumdisplay.php?172-Everyday-Performance-LLC And Mark (Carmantx) http://www.v8buick.com/member.php?13537-carmantx And the 76 Q-jet should be a good carb to build. I would check your ignition timing and make sure it is right. That gets fouled up on a lot of cars because many do not understand the basics. That is why I authored this thread years ago. http://www.v8buick.com/showthread.php?63475-Power-Timing-your-Buick-V8
That core 17056240 is one of the best to start with. The 76+ M4M style carb was another step forward in the design of the Quadrajet, and its calibration requires less monkeying with to get it right. Mark listed three of the big design advantages as well. The ability to adjust the cruise mix for gas mileage thru the top of the air horn is one of my favorite reasons to use a 1976 core. Mark provides quality services, he will do you right. Larry makes a good point regarding the timing. a good powertune of the distributor makes a WORLD of difference in performance and response of an engine. Even the best Qjet will be a dog with crappy timing. You have to look at it as a complete system - tuning all the components to work together is where the best results are at.
I like the later model carburetors and use one on my own engine. It's from a 1977 Pontiac 350, but nearly identical to the 76 Buick carburetor that you have. I drove the car to our local track last Friday night and made a few runs, attached a copy of one of the timeslips below.....Cliff
