1927 Miller Model 91 Racer

Harry Miller's contributions to the motorsport arena include the first aluminum pistons and the potent 'Miller 91' of the late 1920s. The '91' was so successful that the AAA was forced to change the rules to the production-based 'junk formula' to give other competitors a chance. At the heart of the '91' was a 91-cubic-inch, twin-cam eight-cylinder engine enhanced with a supercharger that brought output (initially) to 155 brake horsepower at 7,000 RPM. This figure would continue to rise to over 250 horsepower at 8,000 rpm. Both rear- and front-wheel drive configurations were built, and when in the latter configuration, its low-slung chassis heightened its performance credentials.

Pete DePaolo purchased a Front Driver Miller '91' in 1927 for $15,450, an astronomical figure for the time. An additional $5,000 was given to Miller to make further enhancements. Despite the investment, the car suffered from teething problems, including overheating and failure of the supercharger gears. When it was operational, it was among the fastest cars in the country. A supply of better gears from another company brought the durability he required and won the 1927 AAA National Championship.

DePaolo and Wilbur Shaw drove it in 1928, and Bob McDonough piloted it the following year. It was then sold to Harry Hartz, who reconfigured it to comply with the new 'junk formula' regulations. The chassis was widened, and a Miller 122 engine was installed. Driving duties were entrusted to Billy Arnold, who won the Indianapolis 500 in 1930 and took the national championship for the year.

An accident prevented the Miller from racing at Indianapolis in 1931, and following another crash in 1932, the car was rebuilt and sold to Fred Frame. Pete Kreis drove the car again in Indianapolis in 1933. Mr. Frame drove the Miller in 1934, but luck was not on his side, as the car was involved in another accident. It finished 10th at Indianapolis in 1935, and in the ownership of Mike Boyle and with new Miller engines, it qualified 3rd in 1936 and finished 3rd overall in 1937.

The Miller was finally retired following another accident in 1939, and another rebuilt.

Years later, Chuck Davis was able to resurrect the Miller using numerous parts collected over many years. The engine installed in the bay is believed to be the original DePaolo engine, and the car has been restored to the 1927 Indianapolis 500 configuration by the late Dave Hentschel. The body, frame, tanks, and radiator shell were recreated.

This Miller model 91 was displayed in 2013 at the Amelia Island Concours d'Elegance, where it won an Amelia Award in the Cars of Harry Miller feature class.

By Daniel Vaughan | Dec 2022

By the 1920s, professional race teams had replaced most of the modified stock cars that had dominated motorsports competition through the first two decades of the 20th century. Stock-based chassis and bodies were also giving way to purpose-built racers, such as this front-wheel drive Miller. In fact, the years between 1919 and 1929 are viewed by many historians as the 'golden age of the thoroughbred American racing car.'

During this period, purpose-built racers from Duesenberg and Miller dominated the scene as they alternated wins at the Indianapolis 500 race. In 1924 Duesenberg introduced centrifugal supercharging to the speedway - forced induction by means of a gear-driven compressor. Harry Miller soon became a specialist in this department, applying supercharging to his own racing engines.

This racer was purchased from the Miller factory in California by Pete DePaolo in 1927. Its first outing was in Atlantic City, where it overheated very badly. Equipped with a large radiator, DePaolo then took the car to Indianapolis for the '500.' Several days before the race, the car's supercharger gears failed. These gears were a documented problem in many of Miller's racers. New gears were flown in from the factory, and the resurrected racer was running in second place when this set also failed.

DePaolo then turned to another company for his gears and went on to first-place finishes at Altoona and Salem. He continued to place well throughout the year and, despite all the problems with the car, went on to win the AAA national championship. The car then changed hands several times and was used in the MGM movie, 'The Crowd Roars.' It was then rebuilt several times, winning the 1930 Indy '500' with Billy Arnold behind the wheel.

The car was restored to its 1927 factory condition using the original DePaolo engine and other parts found by Chuck Davis. Dave Hentschel of Hentschel Automotive did the restoration. It is on loan at the AACA Museum, courtesy of The Miller Race Car Collection.

Source - AACA Museum