Well you're smarter than me;Wow, I had forgotten all about that.
I think I only ever saw that screw on a 41xx in a 60s grain truck.That's going on 40 years ago
To tell the truth, on a 4100 series carb, I have only ever had to fudge the vacuum break maybe once.
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My own 750DP carb has no choke at all, and I used to drive it from May long weekend to September long weekend, then pull it out and put the winter motor in. I sometimes stretched it to over 6 months.
I think DPs are like that;fairly rich on the low-speed circuit. They kindof have to be calibrated to a lower vacuum level than your Carter 2bbl,lol. My combos have all pulled from 8 to 12 inches at idle. This last one, with about 10, is right in the middle. You can fine-tune the idle vacuum,and the on-choke fast-idle vacuum, with timing and rpm.
To start it cold; I just mash the throttle a time or two, depending on the ambient temp, and hit the key. Then I babysit it for half a minute, with a blip or two,and that charges up my brake booster. Then she's ready to rock,almost. She takes about 3 miles to start warming up the aluminum heads. During this time the speed increases without my increasing the pedal, so I am actually backing out of the throttle every mile or so, to prevent speeding. I refuse to waste my money on speeding tickets. Since 1999 that car has never gotten a ticket for speeding. Other tickets yes,lol. After three or maybe four miles, she is ready to be abused.