Hard restarting of a hot/warmed up stovebolt engine is not an unusual thing. Built up heat reeks havoc to the fuel in a carbs float bowl once it transfers from the hot manifold to the carb. GM and pretty much all manuf's put carb insulators on to try to prevent the over-rich heat transfer condition that occurs all frequently.
1st thing I'd do is make sure theres an insulator installed then check the float settings. If your carb is a Rochester B model check the power piston for free movement. If it's stuck it's generally in the rich condition. Course it'll give overly rich symptoms at all times.
All that said, which may be alot of hot air, LOL., try the following.
On your next hot restart, while cranking slowly depress the gas peddle all the way to the floor so the throttle plate is fully open, if it doesn't start slowly return the gas peddle back to it's idle position. If the engine is in an overly rich condition it should start somewhere in the peddle return. What you're doing is finding the sweet spot where the air/fuel passing through the carb is the right mixture.
My old 216 would restart during the slow depressing phase but every now and then it wouldn't start until the releasing phase.
Additional causes to making an overly rich warm/hot engine restart is carb set too rich, choke not fully open, heat flapper valve stuck in "open" position, float set too high, someone put in a larger main jet, restricted air filter, using an electric fuel pump with too high a pressure, fouled plugs, timing too retarded, points set incorrectly, valves not properly adjusted to name a few.
Read your plugs, if they're black and sooty the engin eis running too rich.
Good luck
Dave
