Smoking black?

[Classic-Cowboy]

Alright y'all I have a 86 Chevy c20 with a heavy duty 350. Just had to replace the carb do to the origanol Rochester going out. I now have a Holley600CFM on there. It is running ok but i had to turn my float screws out a little bit cause it was over fueling itself but now I am getting a backfire through the intake and blacksmoke from the exaust when I get on it. Any ideas? Trying to make this motor last untill I can get a crate. PLEASE HELP!

 

[bucket]

If it's electric choke, you need to make sure it's opening all the way. If the float level is OK, you need to set the idle mixture screws for highest vacuum and then reset your base idle speed. After setting the idle speed, adjust the idle mixture again and then fine tune your idle speed once more if needed.

The included accelerator pump cam should be pretty close for a basic 350.

 

[bucket]

And make sure there's no vacuum leaks between the manifold and adapter, or between the carb and adapter.

 

[Classic-Cowboy]

Awesome I will start there thank you

 

[philjafo]

Black smoke is usually very rich, make sure your floats are set correctly. Also for checking vacuum leaks I like to use carb and choke cleaner or spray lube, spray it at the base of the carb and at the intake gaskets any change in rpm and you got a leak.