You may have missed some of the point. I ran rods, yf and glass bowel 1bbl on a series of Weiand, offy and a cyclone 2x1 intake so direct to plenum. Ran decent. Ran Holley/Weber 5200 2bbls On same Weiand manifold with adaptors, ran better. If the intake was a 2x2 may have run better. Ran bigger carbs direct to plenum on a Clifford, ran way better. I doubt that the bigger carbs would run well on adapters. It’s all about what the motor needs and wants as to whether direct to plenum makes a difference. A mild built motor might not respond better or worse if carbs are fed through an adapter or direct to plenum. On the other had, a highly modified motor would run better direct to plenum. I think that is what I was trying to say in my inarticulate way, lol.
Carter YFs, pretty good carb. I like them better then running rods. Simpler, easier to rebuild, the early models (think 216 versions, manual choke and the later automaticc choke) are smaller and run better in my opinion on a dual set up. Main jets are the same as wcfb jets or maybe AFB I forget, will have to look at my jet box to confirm, and are still available. The yf uses a rod arrangement to meter idle fuel, and the rods can be swapped around. Never played with the zenith but I have heard they are a terrific carb
