the secondaries should not open/crack open or anything with movement of the center carb throttle shaft. this will really screw up idle/low rpm run. look for a burr or something were the carb linkage screw rides in the throttle arm slot. jimmy jack Studebaker may have put a screw in there at sometime to get the carbs to open sooner and boogered the slot. those connecting rods should never be tight but have a little up and down movement at closed throttle.