The guy in this video talks about how the secondaries on the Q-Jet are somewhat restricted and don't open all the way. He says by filing down a tab will take care of the problem. It's the first 30 seconds of the video. Oh and I know it's not a Buick, but it's still the Q-Jet. So tell me, what do you guys think about his advice? http://www.youtube.com/watch?v=zWJC44oMYbs
One i did not know about . I know about theone to drillout the plastic vacum pull off to let it open quicker and adjusting the Closed spring tentionon the secondary upper plates to open faster , there are a ton of Qjet tricks someone should right a book , with all the different primariy and secondary Jets , rods, arms the combos are endless, Played with them for years Thought i had a good set up , Untill i sent one to John Osboren to do up for me He sent me back a bag of internal parts and a amazing Qjet told him what i was running and it is right on
I can't watch the video, but I know Pontiac set the Q-jets in Firebird 400/455's to not open the secondaries all the way. The Firebird's got the same engine's as the A-body, but to keep with the corporate limit of 10lbs/HP. Pontiac limited HP by keeping the carb from openning all the way. Simple fix =D I don't know if Chevy did the same on the Camaro. Buick's didn't have a big block small car to worry about that.
Someone did, Cliff Ruggles, CliffR on V8 http://www.amazon.com/s/ref=nb_sb_n...Cliff+Ruggles+Quadrajet+carburetors&x=10&y=18
A Good Pair Of Dykes Will Clip It Clean. Once Clipped You Can't Go Back, And A Your Stock Engine May Not Be Able To Handle The Full Monte. Personally I Trim All The Ones I Do, Never Had A Problem.
That is a good mod. Stock Qjets - take the 73 350 qjet 7043244 for example - had large tabs there combined with very lean 2nd rods to limit HP and emissions. trimming the tab a ways will let more air come in when the motor asks for it, BUT I would couple that mod with a richer set of 2nd rods at a minimum, and even better yet some mods to the 2nd fuel delivery openings. Cliff Ruggles' book covers this topic well.
Guys, I can tell you about my GMC Safari van, with the 4.3 V6, and a Qjet, the 750cfm unit. I removed the tab on the secondary air valves, and even that 4.3 improved. I could feel the resulting power post 3500 rpm, especially after putting different secondary metering rods in and resetting the opening rate 1/8 turn looser. I thought that van ran pretty well until I did that. Then it really woke up. If the 4.3 V6 will handle the air from a 750 cfm unit, I am sure that there is no self-respecting V8 that won't appreciate it. I have also made this mod with no shame on more than one Qjet, and never looked back.
Wow. It's good to hear all the positive feed back. It's always nice finding small ways to tune the ride. :3gears:
We tested the opening angle(s) of the secondary airflaps, dyno and at the track. It is covered in our book. We ship them same day ordered, and the ONLY place you can get a signed copy! Tuning the various systems are also covered, along with other HP modifications. The most important information is on complete/correct rebuilding, and correcting any issues with the basic castings that you are working with. Unless the foundation is sound, all the modifications in the World aren't going deliver a good end result....Cliff http://www.cliffshighperformance.com/buy_book_2.html
The high performance early 70's pontiacs, Ram air etc, were letting all the air into the q-jet they could get. They even removed one of the primary venturis on both barrels. No limit on HP with those ponchoes (only ADVERTISED HORSEPOWER was limited). However, they did limit the air valve to 76 degrees (and Big Buicks used 80 degrees). I have heard you get "deminishing returns after 80 degrees", because the air valve blocks the big brass fuel tubes at 90 dregrees. I installed an adjustment screw and set mine at the original BBB 80 and could not see any difference than at 90, so 80 will stay. Would like to hear more info on this: Fuel distribution, A/F ratio, Dyno HP, ET, MPH.
