Car runs after main switch by battery is off

I had that problem on my race car when I first started
(not good for Tech) and found the problem to be the motor was running
off of the alternator when the battery was disconnected. If you have
a two part switch at the battery try breaking the alternator output
wire with the other part of the switch or put a switch in your switch
panel to work on the alternator output. I nolonger use an alternator
so that is how I fixed my problem. Hope this helps.

69 Cuda, 383 w/2 4bbls, Keisler 5 speed, 456 gears, for the fun of it!