The problem is NOT the carb. It is the tuning procedure. 10" of idle vacuum is the problem. It needs a LOT more initial timing. The other problem is that the pri throttle blades are probably open too far at idle, exposing too much transfer slot [ TS ]. This in turn gives a domino effect. Idles too rich, off idle flat spot, because TS is wrong.
You first need to get idle ign timing correct.....before touching the carb.
Unless Edel changed the instructions, they say for low vac situations to use vac adv connected to manifold vacuum.
Before doing that, try this simple 5 min test & report back with the result. Warm up engine, in D if auto trans, engine idling, loosen dist clamp & slowly turn the dist CCW. This will advance the timing. Keep going until you get the highest idle rpm/smoothest idle; toggle dist to be sure. Now check what the timing is & report back.
