Drilling Holes In Carb Throttle Plate Blades

340inabbody said

Thanks sounds like a systematic way to move forward. Two questions. What do you mean by “idle bypass” specifically non-Venturi type?
Also will this affect the in/out of gear imbalance I was referring to in my op?

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Quadrajets have an Idle bypass channel that goes around the venturi that increases the sensitivity of the idle circuit when the factory application requires it. Altitude market (Denver) and or excessive overlap) Say below 16hg. If your not versed in tuning air bleeds, or your carb docent have adjustable air bleeds you can screw up a fixed air bleed carb fairly quick by "modifying the air bleed blindly." idle bypass is the simplest way to see if your having an issue with the over exposure of a transfer slot that is reversible. For instance, say you find that the 1/8" idle bypass cleans up you mildly cam'd engine idle and transition. You can run an 1/8" vacuum line to a nipple you install in the base of you air filter.

But as stated in post #7 there is more going on than just idle bypass. The Idle channel restrictor "air bleed" comes into play once you have the idle bypass in calibration.
GM had .100" + idle bypass on some circuits from the factory! Holley's and Carter universal application carburetors are not calibrated for any increase in altitude and low hg, say below 15 without air bleed modification.

Sure they will run and blaze the tires, but you'd be aghast with an AFR gauge!

If your above 3500' elevation the sensitivity is not their exponentially with an increase in elevation due to the change of atmospheric pressure.