1980 Chevrolet Blazer with new 350 330 hp with vortec heads gm performance motor 12486041 I have a eddlebrock thunderseries carb I am getting black spark plugs and rough idle is it timing plugs both?

Answer 1

Black plugs indicate that you're getting too much fuel. You need to set up the carb and to do that you'll need access to an exhaust gas analyzer. Don't go too lean or you'll burn valves and possibly a piston.

Running "rich" can also cause a rough idle.