Hard re-starting warm engine

[fordfun]

Occasionally my '29 Sport Coupe will stall (die) when stopping at an intersection. When this happens, it's difficult to restart. Eventually, after several attempts with the throttle wide open (and just before accepting a push), it restarts. I believe the timing is set correctly, as I just checked it with a timing light per Les Andrews' procedure. Any idea what might be going on here?