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#1
11-09-2015, 09:41 AM
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Quadrajet Off-Idle Air Adjustment Screw
What does this screw affect? This little screw has always been a mystery to me. Does adjustment out make lean?
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#2
11-09-2015, 09:55 AM
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It adds more airbleed area to the upper idle airbleed, used thru 1969 on many Pontiac carburetors.
It will reduce signal to the idle tubes, so essentially putting LESS fuel to the mixture screws, and transfer slots at any engine vacuum reading. It can be used to fine tune the idle and fuel to the off idle system, if/when needed. It really depends on how the carb is set up, and what's been done to the engine under it when it comes to "fine tuning" using this feature. I prefer to gently seat them, then modify all items related to idle/off idle for the application. Pontiac carburetors thru 1969 use a pretty small upper IAB, so they will typically have pretty small idle tubes and still a generous amount of idle fuel down to the mixtures screws and transfer slots. Starting in 1970, the same screw leads to passages under the MAB's, so has nothing to do with idle, but can be used to fine tune the main system instead......Cliff
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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
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