Help with low idle

My idle is to low and I can't seem to bring it up without coming off idle circuit. When I turn the air fuel mixture screws all way in engine idles better and smoother. Checked for vac leaks can't find any. Checked timing and even tried advancing it a little. Cleaned the carb didn't solve problem. Figured had to be the carb so I installed a new holley with same results. Engine never dies but bothers me cause I hear the dampener knocking. Im not sure what else to check.

I havnt checked that. I have a new longblock only couple years old. Never had any issues but I'll give it a look.