I heard, or was told he had a gas cap (this was before fuel cells) he drilled out for a tire valve stem to be inserted, and after tech inspection he would install the special cap and shoot compressed air into the tank, belling it out, thereby increasing the volume by a few gallons. The advantages to doing this are obvious. If they placed in the money, the
car would retire to the pit area, where a waiting crew member would roll a floor jack under the
car and smush the fuel tank back in. Smokey wrote a book callled "Power Secrets".......very good read. He had probably forgot more information than most of us will ever know.