Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor
Qjet 17057253 on a 380 Olds stroker
Seff:
Seems like I've been banned in the mean time.
77cruiser:
Is this a dual main air bleed?
Seff:
Yes, I believe it is.
Cliff Ruggles:
Nothing wrong with seeing A/F ratios in the 14-16 range at light part throttle and even with a light load climbing a grade as long as the engine doesn't go "flat" or loose power.
At some point engine load becomes great enough and throttle angle increases enough where vacuum falls off to the advance and the power piston raises up to richen things up.
When this happens you should see the A/F ratio quickly drop some and no lag in engine power.
If you have places in the engines power curve where you increase throttle angle and it goes lean, surges, hesitates, etc, then some additional tuning is needed to richen it up in that range or the carb has a fundamental issue someplace.
I've tuned many hundreds of the later Olds Q-jets and never once had any issues in the areas you are seeing problems with. We usually end up with 72, 73 or 74 main jets in them and use the APT to fine tune part throttle A/F accordingly.
I actually use a 1977 Pontiac Q-jet on my own engine, basically identical to any 1976-1978 Olds Q-jet with a different airhorn and it has been flawless for decades. It's also been on 4 different engines with many changes to those engines taking the power level from about 350hp to almost 600hp, and still using the exact same jet/rod combination on the primary side.
My engine doesn't have a working crossover in the intake either so in cool/cold weather it takes a few minutes to heat soak before it's completely happy.......Cliff
Seff:
Cliff, I remember you commenting on your combo before... And make no mistake, I'm grateful for any and all comment!
I think at this point it's prudent to take the carb apart again and measure all parts again, to eliminate the factor of human error when I was building the thing. That's a project for tomorrow.
Would you still recommend third recipe idle system modification? Or take it back to stock?
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