Quote:
I expected that bypassing more air through the outboards would have leaned out the A/F ratio even more than it had been. It actually richened it up and the car is running better than ever now. Can anyone clarify the physics behind that?
I'll give it a shot.

Originally Posted By jbc426
.... After a few minutes, I had the center carb closed up significantly, and the outboard carbs open about a half a turn of their idle screw from fully shut.

It seems like you balanced it. The engine consumes about the same amount of air - at least by volume. The total restriction to air flow is similar or little more than it was before. Enough so that the vacuum at the idle discharge areas is noticible higher than before.
This increase in pressure difference is moving more fuel through the idle circuits. This more than offset any drop in the air mass flow density.

Even at the lower throttle position, it seems likely in this case that the idle jets are still the main restriction on fuel at idle.

I'm curious, are the idle jets on this carb located below the fuel level?

Last edited by Mattax; 03/14/18 10:25 PM. Reason: clarity, I hope!