Analysis of information sources in references of the Wikipedia article "Bernard Pietenpol" in English language version.
By now Henry Ford had come out with his new car, the Model A, powered by a bigger four cylinder engine. At an estimated 40 horsepower, this engine seemed just the thing for Bernard Pietenpol's new aircraft design's needs, and having been on the market for several years, junk yards were starting to get as many of them as Model T engines...So Bernard Pietenpol went to work converting the Ford Model A engine for his new monoplane. In May 1929 Bernard Pietenpol test flew his Air Camper with the new engine. It was a complete success - a perfect match of airframe to power plant.
