Black box missing

hi all just out of interest, does the black box that sits next to the vaccum pot on the distributor make that much difference to the idle on 383 2bbl.
i was looking through my manual and i found that my car should have a ground lead off the carb to this black box which retards the timing at idle , so off i went to look at my set up, and guess what! it aint there! got two screws an a thin strip of metal though ha! any input would be cool bye for now trev
i was looking through my manual and i found that my car should have a ground lead off the carb to this black box which retards the timing at idle , so off i went to look at my set up, and guess what! it aint there! got two screws an a thin strip of metal though ha! any input would be cool bye for now trev