The Pontiac brand was introduced by General Motors in 1926 as the companion marque to GM's Oakland division. Within months of its introduction, Pontiac was outselling Oakland. As a result of Pontiac's rising sales, versus Oakland's declining sales, Pontiac became the only companion marque to survive its parent, with Oakland ceasing production in 1932.
Pontiac began by selling cars offering 40 hp (30 kW) 186.7 ci (3.1 liter) (3.25x3.75 in, 82.5x95mm) L-head straight 6-cylinder engines in the Pontiac Chief of 1927; its stroke was the shortest of any American car in the industry at the time. The Chief sold 39,000 units within six months of its appearance at the 1926 New York Auto Salon, hitting 76,742 at twelve months. The next year, it became the top-selling six in the U.S., ranking seventh in overall sales. By 1933, it had moved up to producing the least expensive cars available with straight eight-cylinder (inline eight) engines. This was done by using many components from the 6-cylinder Chevrolet, such as the body. In the late 1930s, Pontiac used the so-called torpedo body of the Buick for one of its models, just prior to its being used by Chevrolet. This body style brought some attention to the marque.
For an extended period of time—prewar through the early 1950s—the Pontiac was a quiet, solid car, but not especially powerful. It came with a flathead (side-valve) straight eight. Straight 8s were slightly less expensive to produce than the increasingly popular V8s, but they were also heavier and longer. Additionally, the long crankshaft suffered from excessive flex, restricting straight 8s to a relatively low compression ratio with a modest redline. However, in this application, inexpensive (yet very quiet) flatheads were not a liability.
Source: Wikipedia, 2011