i'm in the middle of doing a rebuild of my 72 3 screw SU's and i found that my floats are off and is prob the reason for my car running rich. i would check your levels and your floats for leaks.... they will be heavy if so. You can check these while the carbs are on the car. i also found that i was using to much oil and that it was to heavy of weight. all of this makes the carbs run rich. so i hope that with all these things fixed i will have them on the car tomorrow and i have a uni-syn on the way.