I have a 1984 ford f-150 with a 4.9l 300 inline 6. Im having problems with it idling. When the engine is cold its basically fine but then when it warms up it puffs out black smoke. The only way i can get rid of it is by pressing on the gas peddle. Can anyone tell me how to adjust this carburetor for the proper fuel air ratio. By the way it is a ford 1 barrel carburetor. Thanks

 

Those carbs have a power enrichment circuit in the fuel bowl. When the diaphram gets a hole in it fuel will be drawn into the intake by the vacuum under the diaphram. Engine runs rich. Overhauling carb. will fix this.