I was taught years ago to set ignition timing and tune the carburetor in gear with an auto trans, even with a stock engine.
My typical RPM drop ranges from 75 -100. I've had some at only 50 RPM drop.
Click key start and ready to romp.
Agreed! I read it here first and once I actually did it that way my results were way better. It is also 100x easier to hear and feel the engine respond to minor tweaks. When it's just idling in N with no load it's easy to get lost in the settings and have it 'sound good' but then it either dies in gear or wants to creep hard against the brake pedal.
I did the 'adjust idle mix for best vacuum' in N first and it just wasn't right. But then when I did it in-gear I kept gaining rpm as I richened it and wound up 3/4 of a turn further out and the curb idle closed almost a full turn.