Technical Edelbrock 1406 only idles on primary circuit... Questions? Ideas?

I've pulled apart "new" edelbrock carbs and had incorrectly adjusted floats.

 

Same.

It may not necessarily be a production issue. I have seen how my local carriers treat packages.

Many times what I have ordered appears to have not arrived via truck, but via trebuchet, or long-range artillery.

 

I also wonder if the problem was exasperated by having the floats have a slightly different style than original. I ordered replacements off amazon and note that they sit in a different position than in the photo gimpy showed. Almost as if the attachment point where it brazed onto the float body is a touch higher or lower.

 

PCV valves are maintenance items, too. A shot of carb cleaner or replacement should be routine.
Everybody probably knows this but a nudge once in a while never hurts.

 

I think this is a concept that a lot of folks aren't aware of. The idle mixture screws do not control the flow of strictly liquid fuel. It would be too difficult to accurately and consistently meter the small amount of fuel needed for a lean idle mixture.

Instead the idle mixture screws control the flow of an air and fuel emulsion. Essentially, a lot of air is pre-mixed with a small amount of fuel to supply a "pre-leaned" fuel mixture to the idle mixture screws. (See Gimpy's illustration of the idle air circuit a few posts above.) Instead of raw liquid fuel, think of it as a "fuel-foam" solution. This is accomplished with the idle air bleed circuit.

As an experiment sometime, find an engine that has a steady, smooth, normal idle speed. Then locate the idle air bleeds for that particular carburetor and slowly cover them with your finger or a small piece of tape and see how it affects the idle quality. You'll likely find that the mixture screws will no longer have the correct range of adjustment to restore a proper idle mixture.