That annoying just off idle stumble can be hard to pin down. As mentioned above, the accelerator pump must work, right now. Other things to look for include, the "power valve". That lovely long spring loaded bit. It must be free in the the hole. Only vacuum to move it. I "polished" mine with 600 grit paper, and a hand drill. As soon as it was free I stopped. The check valve in the support must fit free as well. Then to finish(still had a stumble sometimes) I added a 1/4 turn(rich) to the air bleed screw(from the book setting) and retarded the ignition just a bit. Those things worked for me. For some reason my truck(55-62 235) pulls a bit less vacuum that most. Close to 15 inches at idle. Steady and working, just less than others I have worked on. I have looked at air leaks, none found so far. Head has been off, and valves checked(good machine shop) and they are good. My gauge on different 235 shows closer to 17-18 inches so not the gauge. Heat riser works as it is supposed to. But with the little adjustments it runs and starts very well. Gas mileage is not too bad(about 16-18) and it runs strong. I have not replaced the Carb, It works so why would I? It does hate dirt. And that has been my only issue. So I have 2 fuel filters, one before the pump, and one before the Carb. They have helped make it reliable and fun.
