The q-jet on my `67 GS Convertible has a flat spot or bog i shold say when i`m increasing into the throttle,i know its not the original Q-jet,i think its off a cadillac or something,what can i do to stop this?i adjusted it as best as i can with vacuum gauge but still doing it,can i purchase a rebuilt kit from somewhere?any suggestions?dont know too much about these carbs as i`ve always dealt with Holleys. Thank you
It could be the air valve tension spring for the secondaries. This is on the passenger side of the carb. There's a set screw and a slotted screw. Hold it in place with the slotted screw as you back off the set screw. Tighten it about 1/8 of a turn. See if this helps remove the bog. If not, try another 1/8th. It could be that the secondary air valve is tipping open too early. I had this problem with my 71 GS455 after I changed to a Performer.
It's on the passenger side of the top of the carb back by the secondaries (where the air valve plate hinges). Here's a pic with the set screw and slotted screw circled off a 76 Buick QJet (only one I have at hand). The set screw aims down from above and the slotted aims towards the passenger side of the car.
Sorry George, I posted this just before watching a dvd. You'll want to put your screwdriver in the slot and hold it while you loosen the set screw, since it's under spring pressure. Tighten it clockwise to add more tension to the air valve. This should delay it from opening and is what helped me get rid of my bog. Loosening it makes the air valve open quicker, which seems like it would be good, but it doesn't allow a smooth transition into the secondaries - thus the bog.
Steve,still the same problem,i had to take the carb off because i turned it too much and the spring came off,i have it as tight as i can before the spring falling off but still getting the bog or flat spot,what else can be causing this? Thanks
George, Typically when a carb. bogs it's because you aren't getting enough fuel in the mixture at that point in time (why turning the air valve may help). I've never tried to tune a quadrajet, only my demon, but I'd go along the lines of your mixture, your accelerator pump may need some adjusting, or something else along the lines of air/fuel. I tend to believe if you were to buy a rebuild kit you would probably have a rebuilt carb with the same problems, but that's just the way I'd look at the situation.
George make sure that your vacuum choke pull off is good and not shot. If that is bad it will allow the back secondary doors to flop open. Good luck Rick
I'll second Rick's analysis, this sounds like the infamous secondary pulloff failure. The seondary pulloff should be all the way in at full vaccum, and then pop out in just over 1 second. If it does not do either get it replaced. Test it with piece of vaccum hose that you can suck on. NAPA is just about the only parts place left that carries secondary pulloffs. Note that it is the pulloff, not the spring that regulates the air door opening. the spring is only a damper and should only be tight enough to let the doors close. If the air dam cannot be adjusted to correct the problem then go for a total rebuild. It's about $60 and will really improve the idle and WOT power. Ifyou're unsure about doing it yourself, talk to John Osborne about getting a rebuilt one for your Buick, he's the best in the business. 270-737-4467 JOP455@AOL.COM Some more info for you based on the 7027231 number: 70: the carb is a pre-smog era unit. 27: 1967 Carb. 2: 49-state emissions. 3: Cadillac. 1: Manual transmission setup.
Where or what is the secondary choke pull off?sorry guys i really dont know sh@t about these carbs. Thanks
George they are the little round things on the pass side that have vacuum lines to them. The Buicks have 2 I don't know about the Cad ones. If its bad your motor will bog like crazy out of the hole and take off like a raped ape. Rick
