Found it!

hehe i just saw on mythbusters they tested the old "hole in the gas tank - flaming trail of gas" myth and its basically busted. you have to be creeping along under 5mph for the burning gas to catch up with the car. the faster your going the less gas is being laid down anyway so it slows even more. also they tested the tank explosion and couldn't get it to explode, the gas just burned inside the tank.
of course i still can't quite get up the stones to smoke around the gas tank.
-tim