I just got a classic Ford 8N tractor running again. Someone trying to be helpful flipped the battery around, connecting negative to ground. This made the engine crank backwards! So I had spark, compression, and fuel but it wouldn't start. This got me thinking:
Positive ground was very common, especially on 6V system on work machines. Today almost all vehicles are negative ground.
Is this just a matter of convention, or are there reasons to choose one over the other?