Bernie since you spoke of a front and rear carb but no middle guessing you have a 1968-1971 car--right? In any case the float has sunk or stuck. Pull the bottom off the carb and take a look. 6 slotted screws and a gentle twist/pull. Inspect your sealing ring on the brass plug and your gasket prior to putting it all back together--you can get a new set when you order your float.
