I like the bulb idea... a manual mechanical pump!
Beyond the obvious "personal tolerance" for cranking duration, I think extended cranking isn't great for journal bearings. They need to spin to build an oil film. When stopped and at low rpm, they will effectively be metal on metal. The oil will reduce friction, but in general, I think running bearings without a hydrodynamic oil film is a bad idea.
I'm sure there was a design goal for maximum cranking time before starting. This was probably more about perception than technical considerations but I doubt they wanted a car to crank for more than 1 or 2 seconds under "normal" use. They certainly knew a car could sit for months and would take a long time to refill the carb, but this was not the "normal" scenario. Generally, if you buy a car, you intend to use it.
So here are my measurements from today.
This is a stock '70 350 with a '69 Buick QJ on a '71 cast iron manifold. The mechanical pump was new in 2023. The carb was repaired and set up by Shaker455 (Jeff) and both the choke and fast idle are close to "right". The battery is strong, the starter sounds strong. I think it has a 160 degree thermostat.
The car has NOT been started since Oct or November. This means the bowl was empty. I can't prove it, but it was empty. Evaporation happens.
I pulled off the air cleaner and left it off. I taped a thermocouple onto the carb base to monitor the temperature.
To start it, I pressed the pedal to set the choke and fast idle. Then I cranked in 3 to 4 second intervals, starting and stopping a timer each time. I pressed the pedal after every interval to give it a pump shot when gas made it to the bowl.
The carb base temperature when I started was 52 degrees.
It cranked for 16 seconds before firing. It took 4 pedal presses and started on the 4th cranking interval.
I let it come up to temperature by idling for about 20 minutes. The thermostat opened, the choke opened, all normal. Then I shut it off.
As Kenth reminded us, the carb base got hotter after I shut the engine off. When I shut it off, the carb base temp was at 84. After sitting for 45 minutes, the temperature had climbed to 108 and then started falling.
2 hours after shutting the engine off, I pressed the pedal and started it again.
This time, it started instantly... it cranked for less than half a second.
So after 2 hours at elevated temp, there was still enough gas to start quickly. I have no idea how much evaporated, but the carb was NOT dry.
I will check again after 24 hours, then maybe a week, etc.. to see how long it takes to totally go dry again.... remembering it's winter, though...
Mike