I'm not sure if anyone has used one of these, I hadn't heard of them before yesterday. Summit has taken the basic concept of the Autolite 4100/4300 4bbl carburetors and updated it with center-hung floats, sight glasses to set fuel level, and Holley-style jets to build a 600 or 750cfm carb at a pretty friendly price point. Dad was a huge fan of Autolite carburetors. He felt they were about as simple and effective as you could make a carburetor. Of course, that simplicity also meant they were very specific to the engine they were built to sit on. Holley jets would change all that. https://www.summitracing.com/parts/sum-m08750vs
I have owned a Summit 650 vacuum secondary carburetor for a number of years. It is a great street carburetor requiring little maintenance. Not a competition carburetor. Just my opinion.
I've always tossed them.... Waaayy back a friend had a 4300 on a '70 Cleveland Mustang that was impressive. Of course, his dad worked at Ford dealer so knew the tricks to make them sing. The 4100 are bout simple as they come. I used to run a 470 CFM from 289 on a 64 Galaxie 390, was far more responsive than the original 595 CFM. Those early 390 would valve float at 5000, didn't need the bigger carb. It'd jerk the secondaries open like they were mechanical. I rebuilt a 356 CFM, 2100 (from 351) and installed it on my 302 Fairlane. The 289/302 2bbls were only 287 CFM. Because it has long tubes & dual exhaust, made noticeable difference. The dirt track roundy round Ford boys search out (or at least used to) the '66/'67, 424 CFM 2100 that was on 390 for class racing. That was the largest 2bbl version made. Has 1.33 cast in housing, 287 cfm have 1.08 & 356 cfm, 1.23
