318 Carbs?

Carter or Stromberg? I would run the idle screws in all the way (gently) and count the turns then back them out all the way. Use a good spray carb cleaner and squirt it into the screw holes a few times at intervals long enough to let the chemical do its thing on varnish etc. If you have compressed air blast it through the idle screw holes too before reassembling to original turns off bottom. Fill the carb bowl with the same spray through the bowl vent while you are letting the idle circuit soak. When you start the car again rev it up and force the choke closed at the same time which can remove some deposits or debris in air bleeds etc. If this doesn't get it done it is time to at least take the top off the carb and see what deposits are in the bowl and pump well. It is a better thing to just go ahead and remove the carb since many people have dropped screws into their intake fixing carbs while on the engine.