Sounds like typical Stromberg characteristics to me. Because the Strombergs only "choke" one carburettor, everything better be damn well in order to ensure starting. First make sure all the ignition is sorted: good points with proper gap/dwell, good plugs with proper gap (at the top of the .025-.028 spec) and make sure the distributor bushings are not too worn; with a .010 point gap it does not take much bushing slop to negate that. Next, make sure the choke cable is pulling the linkage all the way open. You may assume that, because the cable is moving,you are getting enrichening action. You might be getting only fast idle action, which does you no good on a carburettor that really isn't working until the motor is running (variable venturi, no throttle pump). The single choke concept worked not bad as long as everything was in order; check it out.