Cliff's Quadrajet Parts and Rebuild Kits
Quadrajet Problem Solving => Diagnose a Quadrajet carburetor problem => Topic started by: Seff on May 01, 2014, 12:30:33 PM
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'72 Olds 350, HR-kit rebuilt '77 Q-jet. Runs well, except when going to WOT - at that point, it bogs when it reaches 3000-3500 RPM, falling ~1000 RPM before it picks up again. Happens from a standstill, and when going from 55 to 80 MPH with no change.
Currently the power piston rod is in the inner hole. Or am I looking at secondaries opening too soon/too late? The choke pull-off works well and doesn't leak.
Thanks, Mark.
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One thing you can do if you want to know if you have a problem in the secondaries or the primaries, temporarily [and carefully] lock the secondaries closed so you are only operating on the primaries. Good luck and keep us informed....
Once you dial-in the secondaries on a Q-Jet, you may find you need better rear tires!
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Choke pull-off release time and spring tension on the secondary airflaps play a role here. How quick is the pull-off, and how much spring tension?....Cliff
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I'll get back to both of you with info on all of that. Right now a slack timing chain job has the engine halfway apart.
I CAN tell you that it's the factory pull-off. Do you suspect it's a lean or a rich condition I'm experiencing upon WOT?
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In most cases a "bog" going to full throttle is a lean condition, as it takes a heap-ton of fuel to flood out an engine enough to cause a "bog". In most cases overly rich results in no real noticeable issues going to or at WOT, just not ideal power output.....Cliff
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Gotcha.
I tightened the secondary air valve spring an 8th of a turn at it helped, so another 8th of a turn will be attempted.