black smoke at start up

[57rookie]

I have a very stock 86 GMC with the 305 and the 4 bbl quadrajet factory carb. It has a full tune up as I am restoring it and have put new plugs/wires,ect. on and it runs very well and idles well when warmed up but at start up it is choking its self and blowing black smoke out. I have heard that this is because my secondaries on the quadrajet are probably out of adjustment and are completely shut choking the engine of air. I don't know how to adjust this on a carburator, does anyone have tech info or pics to show me where I would adjust this. The truck runs so well once the electric choke finally seems to take hold but the black smoke and chugging at start up is very frustrating. Engine has only 60,000 original miles.
Thanks to anyone that can help.