Few car companies enjoyed the same success over the same long period that Pierce-Arrow did before 1920. In 1918, Pierce-Arrow increased its stake as the premier luxury American carmaker by introducing a new 66 horsepower engine. It retained the same 825 cubic-inch displacement and 6-cylidners as prior models, but increased the power with 4 valves per cylinder. The 'dual-valve 66' was also the first American car to feature four-wheel brakes. Only four prototype cars were built with this new engine and were reportedly sent to dealers as demonstrators. This 7 passenger touring is the only surviving example of the four dual-valve 66 Prototypes.