[Ed in Maine]

Just to add another variable to this discussion, it also depends on the size of the Main Jet. Published flow data indicates that this jet (which is directly connected to the carburetor bowl) is 150 ml/min to 160 ml/min. I have found that when I rebuild a carburetor that has a Main Jet calibrated at 160 ml/min, that it greatly reduces the need for the GAV to be open. Note that the GAV is putting gas into the Cap Jet that is next to the Main Jet in the carburetor throat. Well, this is no fun because part of the fun of driving a Model A is adjusting the GAV to meet the driving conditions. Now, I strive to set the Main Jet at a flow rate of 156 ml/min or less down to 150 ml/min so that some supplemental gas from the GAV is required. I like J Franklin's take on all this, "the GAV will be at the clock position it needs to be". Ed