Have '81 f250, 300 six w/offy dp, holley 390, efi duals. Timing is set as 12btdc, which is where I want it to be. The idle can't be adjusted below an indicated 950 rpm on my tach, and the idle speed screw is floating free. Other than retarding timing, can anyone tell me if there are internal adjustments/substitutions to the carb that will allow me to get the idle down to 650rpm or so?
