help!!!!Truck is running bad

[the fall guy]

My 85 Blazer is running horrible. especially when cold. It is all stock [305] but has a holley street avenger carb on it. When it is warm and i hammer it....then let off....a puff of black smoke comes out the tailpipe [is this normal???]. When i take off when cold it stalls and sometimes it burps through the carb. Any help would be greatly aprreciated.

 

[James670X]

Black smoke can be caused by one of two things, 1. Too much fuel (ie. running rich) or 2. Blowby (valve seals or piston rings are gone).
Personally what I would bo would be a complete tune up on the thing (ie. new spark plugs, wires, cap, rotor, 02 sensor if so equipped, pcv valve, air cleaner, crankcase filter, check the timing, etc, etc...) and then I would look at the carb and see if it's jetted properly, an egt guage or pyrometer will help you in this department.