For 1926, the regulations covering Grand Prix racing further reduced the allowable engine size to 1.5-liters, or 91 cubic-inches, for supercharged engines. The Indianapolis race adhered to these rules and the cars produced in Harry Miller's shop for the new formula represent, in the option of many historians, the pinnacle of American racing car design. While Miller was also building front-drive race cars, they were only suitable for Indianapolis and on board tracks; those wanting to compete on dirt tracks opted for the conventional rear drive layout. The 91 cubic-inch engine was similar in appearance to previous Miller straight eights, with every component part reduced in size and weight to the absolute minimum. This example has Miller Engine No. 6 (of just seven built) and correct transmission and rear end. In recent years this car has been a frequent participant at the annual Miller gathering at the Milwaukee Mile.