We have custom drive in airbleeds for those carburetors.
The large MAB models are difficult to bring in range across the engine speed/load range. They just don't make jets big enough for them, so we install the smaller MAB's and smaller jets and metering rods.
We see a LOT of those carburetors in here where folks have made a lot of engine mods and they are not working well. Many come in with the main jets drilled to .080" or larger. There is simply too much emulsion air. They work OK with stone stock applications, with all the emisson control devices hooked up and operational, but that's pretty rare to see these days. Most engines have been rebuilt, bigger cams, free flowing exhaust, cooler thermostat, more compression, etc, etc.
What happens when the smaller airbleeds are installed, is that the signal to the main system is improved, and less air bled into the main fuel supply to the nozzles. This just makes it much easier to give the engine the A/F ratio is requires. We've had perfect success doing this, and still have full contol of the primary side A/F ratio for best efficiency, smog testing, etc.......Cliff
