As pointed out already the stock fans and belts draw about a tenth on small blocks - and back in the 70’s it was common on a few cars to purposely misalign the alternator so in a burnout you would blow the belt off, effectively running down the track without the belt.

Usually done on class racers or when running a tight race against a similar class car in the eliminator.

Back then the rules said everything had to be stock and hooked up. Rules didn’t say they had to stay hooked up - another “read between the lines” interpretation.