What's the most expensive thing you ever screwed up because of a personal brain fart. Being a car person that's where my chance at mayhem is most likely to be. It can be trains, planes, or automobiles, or tanks, or boats. You know, like McCain almost sinking an aircraft carrier, the one he was sitting on at the time. Up until 1931 most car had either gravity fuel system, or a large can on the firewall that used engine vacuum to pull fuel into it, and it in turn fed the engine through gravity feed. A lost of the old cars have been fitted with electric fuel pumps to fill the tank, at whick point YOU SHUT OFF THE ELECTRIC PUMP. Well, we were trying to start an eight litre Benlley that our boss had just paid almost a million dollars for. I showed my bud, who was starting the car, where the electric pump switch was. I assumed he would shut it off after a little while. (You know that old saying about assuming) Another feature of the tanks was a filler cap to fill it if it ran dry, for those of you who are not lazy like us. In that filler cap was a tiny vent hole which, when the tank got full, started spraying that gasoline in in a fine pre-atomized vapor. Directly beneath that tank was the magneto, full of electrical sparklies. When the engine compartment wa full of vaporized gas my but turned on the ignition and hit the starter, causing that magneto to start creating sparklies. When that vapor ignited it blew both hood panels open and there was fire shooting out all the louvers and around the hood panels. Luckily, being a vapor fire it quickly ran out of fuel. I don't know why we didn't destroy that car, God protects the feeble of mind, I guess. I didn't do it, but my brain fart was not reminding him to turn off the pump.