1. While the question is hypothetical with the -40 for 3 days, the reality is it doesn't take 72 hrs to chill the engine down to the ambient air temp.
2. I am pretty familar with weather data, and even outside of that I can say with great confidence that I have had to start my truck several times at temps in the -35 to -40 degree range. It sounds like you just dumped your tool box onto the shop floor for 20-30 seconds, but she has never failed to start if I have good batteries.
