The Pierce-Arrow's engine displacement started at , continuing to a massive and was increased later to , at the time making it by far the largest Otto engine offered in any production automobile in the world. In 1910, Pierce dropped its other 4-cylinder models and focused exclusively on 6-cylinder cars until 1929. The model 6-36, 6-48, and 6-66 continued for the next decade. Starting in 1918, Pierce-Arrow adopted a four-valve per cylinder T-head inline-six engine (Dual Valve Six) and three spark plugs per cylinder, one of the few, if only, multi-valve flathead design engines ever made. The company did not introduce an 8-cylinder engine until the 1929 Model 126, and a V-12 engine was offered in 1931 until the company closed in 1938.