[Bobcat]

To answer your specific question on the power valve .... divide the idle vacuum reading by 2 and add 1/2 to get a starting point for the power valve.
Looks like you`re close . X2 on the ignition . You can`t get the carbs right if the ignition isn`t correct . Again , X2 on as much initial advance as you can get away with ... and limit your max advance to 36 to 37 degrees . I have a Ponds 482 , single 4 bbl and run 26 degrees at idle and a max of 37 degrees with no run on or kickback .... BUT , every engine is different . I bought some different bushings for my MSD distributor that allow larger initial advance and yet limit the max to either 10 degrees or 14 degrees plus initial depending on the bushing selected . Learn to read your plugs ... they tell you what the engine wants/needs/has .
Again , ignition first , then carbs .

Bob