To the original poster. I apologize for hijacking your thread. You have a neat period accessory. I'll stop with this reply.
Dan
In my experience, you want to keep the fuel levels high, not low. IF you should have the misfortune of running the bowl dry under WOT, you will "backfire" through the exhaust.
Stock bore, ex-Le Mans Shelby team GT40 heads, Le Mans cam, headers, and 11.6:1 SCR.
12.7 - 13.1 AFR during a long WOT run and the fuel pressure only drops about the width of the pressure gauge needle so the stock pump keeps up just fine on a hot summer day. Filling the bowls after an over night or longer dwell restart takes some seconds where there is only about 1 to 2 psig of fuel pressure at the fuel log indicated until the bowls fill so there is plenty of float drop. I am using 2.50 valves out of a SA customer's 1965 race engine.
Multiple issues can lead to high rpm WOT lean conditions, live running fuel level is just one. As long as the main starts as soon as you pass the last transition port and doesn't stop until throttles are closed again, that is all that is required and that is easy to check (oxygen sensors systems are real handy).
I assisted two Cobra owners that were running out of fuel to the point of engines died over about 4,000 rpm and in both those cases they had kinks in the fuel line between the pump and engine and didn't know it. Reworking the lines into long curves did the trick. When we bought out red car it would run out of fuel with a small 4V the first two drives around the neighborhood. You may have guessed, but a hose between the pressure regulator the former owner used and the carburetor was way too long and doubled into a kink against the left side inner panel. Shortening that hose solve that one.
One of the most troublesome details about these carburetors is doing the bench needle valve and float settings E. Weber outlined only gets you running. The factory literature indicates that you were suppose to check the actual liquid level and adjust as required. Every 0.001 inch change in needle valve setting, gasket thickness, or float tang setting means a 0.005 inch change (in significant figures) in wet fuel level. I laid everything out in CAD to test the math and then we did of experiments with a carburetor in our car. It worked perfectly and made changing levels a math equation and a few minutes to make the changes and verify the results.
One day I weighed and measured all the floats for three sets of carburetors. I tried to check the angles of brackets to floats the best I could. I picked the six closest to each other in every way and sequentially installed them into a single carburetor. The body had an external sight gauge installed. Surprise. The live fuel level with three floats was within experimental error the same. One float produced barley higher liquid level. One float provided slightly lower fuel level; I would not have tried to change it. One float allowed so much fuel in the sight gauge overflowed. We made several repeats and even tried that wild float in the car. The wet fuel level range I could measure was 0.4 inch lowest to highest with six floats I tried to match by physical measurements. One carburetor six floats and different results. I suspect that is why the E. Weber company recommended check actual fuel levels in the car.
I experimented with that wild float several hours one day. My conclusion was that the bracket attached to the float was bent a few arc seconds from where the other five were. I tried changing that angle a tiny amount but always over shot; one bend would make fuel level super low and the next might have fuel over flowing. The only solution I could think of was design and build a fixture with jack screws to slowly adjust the angle until live fuel level matched the others. Interesting idea but not a priority to spend more time on as floats are cheap relatively speaking.
Bystanders around when we start the car are typically disappointed that the engine is easier to start cold or hot than most stock 289 powered cars of any kind, cold or hot the engine settles into a smooth idle quickly (no jabbing of the throttle or extra rpm required), and running at idle it is not as loud as most of the 1960s hot rodded cars they might know. The mechanical valve lifter and rocker arm sounds are the only clue the engine is not a demure stock 289 2V Fairlane engine. Some seem to be disappointed that leaving a parking place takes no more effort or created no more drama than leaving a parking spot in our 2015 Ford F150 pickup truck. In all respects except fuel mileage the red car with 4-2V is much easier to use than the black car with 4V. I used to think the black car was quick. It would out run anything small block with fenders at Hallet except GT40s and a Genie sports racer somebody use to bring. The Pantera with Webers that showed up one year sounded good but it was not tuned well and I passed it. The red car with 4-2V makes the black car seem like a really old antique with a four cylinder engine. The red car is fun but took a lot of development and learning to get there for all around ease, great manners, and exciting acceleration. It was fun to experiment, develop, and learn. I don't know that I would do another engine though. The plug and play fuel injection systems make life so much easier especially if you drive been near sea level and the top of the Rocky Mountains and use whatever fuel you can find on the road.
I tried using 4-2V just as SA put the systems in use. The engine was a fine on off switch but road manners were horrible. Right out of the box as new WOT was fine, every other situation left something to be desired. These systems won't be worth the effort to many people and they won't like the nasty manners they had as SA used them.