Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

Which Recipe Best For My Setup?

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Tinkerman:

--- Quote from: Cliff Ruggles on August 30, 2021, 03:51:24 AM ---What size were the upper and lower IAB's when you took the carb apart?

What size MAB's?

Did they clip the post off the power piston or is it still there?

--- End quote ---

Upper Idle Air Bleed was 0.077". It was that size at the start. Lower Idle Air Bleed was 0.050".

The Main Air Bleed (Main Body) was 0.050" and the Main Air Bleed (Air Horn) was 0.050".

I am not sure what you mean by the power piston post. I think the power piston (accelerator pump?) is fully operation to include the external vent used in 1969.

Thanks,
Dan

tayto:
why run a hotter plug? i thought that as you increase compression you should run a colder plug?

Cliff Ruggles:
The power piston has a metal post sticking out of the bottom of it.  That is part of the APT system and adjusted via a screw in the baseplate.

I would have left the LIAB at .050" since the upper is at .077".  Opening up the LIAB with a large UIAB kills the signal to the idle tubes requiring larger ones and you may have to open up the DCR's as well.

I would have also left the MAB's at .050" at both locations and used something closer to the original calibration.  Pretty sure that carb was .067" for main jets and 42B rods.  The rods were raised to the optimum point using the APT.

Another good idea is to remove the APT screw from the baseplate.  I make a custom external screw in the lathe.  This will provide full control of the part throttle A/F once the carb is placed in service without having to take it apart and changer metering rods......

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