I have that carb in a box in my garage. lol Mine was on my Nova when i bought it & someone removed the top to do something & reinstalled it incorrectly bending the hell out of one metering rod. bent so bad it hung up the float on that side. They are a good carb if you know what to do when tuning.
Now your case---1st pull out the idle mixture screws completely & use carb cleaner & compressed air to clean out idle passages.
2nd reinstall & set idle speed no higher than 550--600 rpm to make sure the throttle blades are not in the transfer slots yet.
3rd use a vacuum gauge to adjust mixture screws---this worked well for me . I've done carb work for 40 years so i set float levels ---bought the Edelbrock kit with rods & jets & springs ---had a good time tuning. Mine was a 1406--mechanical secondary--electric choke unit. They work nicely if you use the 1405 chart to tune them with the different rods & jets. Much richer mixture.