Ok Bob your wrong. First, the subject is not AFB but Hemi AFB specifically 66-67. There is no secondary discharge pickup tube. Just a hole in venturi and it is offset to the side. NO WHERE near the center strut, and the strut does not have a strut bleed. Only carbs I have seen with that were Cadilliac AFB. Secondly, the rear carb does not have the cut out on AV. Besides any tubes like that are in the fuel well of the body. So it is not a cutout for the Secondary discharge. It is centered under main strut for main feed. I am sure it allow main fuel to have a clear path into the air stream, but not all AV had it.
Yes the air valve is like vacuum secondary on a holley in that it does not open until demand from the air flow and DP. Difference is it is another throttle valve in the flow. With an offset angle blade.
Here is a hemi secondary venturi. Just the main pickup tube. Notice the discharge port on the wall of the venturi way off center. With the large pickup hole on the opposite side. The smaller hole is actually covered by a lack of transfer hole in body of the carb. Also as I stated earlier it is a separate circuit from the main, so it does not act as an air bleed one main is on. They are not connected. Plus only one venturi on the rear hemi has the discharge. They other does not. Solid. Again distribution issues. The front does have it on both.
I have made it a hobby to study the AFB especially Hemi. So I am not speculating. You may have tuned but did you test on a dyno and measure AF ratio cylinder to cylinder. Chrsyler did. It was all about distribution improvements as they moved from 66 to 71. Also, 68-71 are different. They are AFBs that actually have a secondary idle circuit. Rear carb only.
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