Black Smoke, have to screw idle/air all the way down

[ubtripn]

I have a fairly new 350 - was told it was a 383 stroker but it started life with me as a mystery crate engine I got for next to nothing. Anyway, at idle it was leaving black soot on the curb. So I thought it's running rich. It has an 800 Edlebrock so I think it is probably overcarbed but I went through the air/idle tuning by turning the 2 screws all the way out then back in until it is where it should be. Problem got worse, I only got it to improve when I turned the screws all the way clockwise. Strong, instant throttle response as before but no soot at idle or black smoke. BUT When revved fast I still get black puff of smoke which I think is unburned fuel.

Anyway, I read that running too lean is damaging so I backed each screw one half turn back from fully seated. Runs fine, does not smell like gas unless I put my foot in it when I get the black smoke so I basically got most of what I wanted until I can carb it with what I want.

The question is, is it even possible that I am running too lean right now? How can I be getting any black smoke when hitting the throttle hard if both screws are fully down?

I am not that great with carbs, if I keep my foot out of it I got what I want but I need your opinions, thanks folks.

My main concern is that I am not damaging the engine running this way or too lean, it does not act lean, thanks.