AC Spark Plug was a separate company and is now a brand of the General Motors Company. It was founded in 1908 by Albert Champion and Billy Durant in Flint, Michigan. It's industry was spark plugs which latter turned into automobile parts in general. It's headquarters later switched to Grand Blanc, Michigan. In 1927, AC Flint became a part of General Motors and later in 1974, it merged with United Delco.
Champion Ignition Company (1908-1908)
AC Flint/ AC Spark Plug Company (1908-1974)
Fire-Ring Spark Plugs