back firing and cutting out?

accelerator pump in carb, air leaks into manifold,incorrect ignition timing,high resistance in leads,incorrect valve timing,faulty inlet valve,cross firing,incorrect fuel grade,incorrect valve timing,idle speed too low/too lean..
try those..good luck :)..(generally it will be a lean misfire)
btw.. if it has a kettering(points)distributor, check the gap/dwell and point contact surfaces

pomandrew
April 2009