1927 Miller Model 91 Racer

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 onboard 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.

The Miller 91 was built for competing on board tracks and at the Indianapolis 500 during the 91 cubic-inch displacement formula that existed from 1926 through 1929. The Miller team had reinvented American race car design with the simplistic jewel they introduced in 1923 for the 122 cubic-inch formula, and the 91 cubic-inch version, which was mechanically and aesthetically fine-tuned, followed. The Miller 91 was very successful and a dominant tour de force of rear-wheel-drive racing technology. In fact, they were effectively responsible for their own demise. In 1930, the AAA introduced rule changes to the 'Junk Formula' to stop Miller 91's seemingly unstoppable winning streak.

This example has Miller Engine No. 6 (of just seven built) and the correct transmission and rear end. In recent years this car has been a frequent participant at the annual Miller gathering at the Milwaukee Mile. The current owner began this car's build after purchasing a Miller frame in May 1992. Although it was impossible to verify the chassis' authenticity, the specifications and dimensions were nonetheless correct, making the frame a perfect foundation for a Miller 91.

Decades later, when early Miller racing cars were sought by enthusiasts, there were no whole 91s to be found. So this car was constructed in the early 1990s around an original engine, gearbox and rear axle components as well as other parts. After paying $55,000 for the rare 91 engine, it was given a complete refurbishment which cost an additional $55,000.

An original Miller gearbox also proved to be difficult to find, as they were made in-house in low numbers. One example was located, and although the owner had refused several offers for the transmission over the years, he eventually relented and sold the unit. Upon receiving the transmission, it too, was sent for refurbishment.

With a correct engine and gearbox, along with an original 91 rear end, the project was turned over to race car expert Bob Willey, of Moline, Illinois, whose father was one of the original Kurtis Kraft dealers. A new aluminum body using Harry Miller's original blueprints was built to cloth these components.

For the external finish, one of the original Miller 91 examples was chosen - the car purchased new by Harry Hartz, which was sold to Mike Boyle in 1926. The car was painted just as the Boyle Valve Special, and it wore #15 when it started 6th on the grid at the 1927 Indianapolis 500, where it finished 19th.

Upon completion, the car was brought to the 1995 Pebble Beach Concours d'Elegance where it received a second in class and Automobile Quarterly's Best Racecar Award. The following year, it participated in the Goodwood Festival of Speed and the Meadow Brook Concours d'Elegance, where it won its class and the Peter Helck Trophy. The car has also been displayed and run numerous times at the Miller Meet in Milwaukee.

The #15 Miller Boyle Valve Special raced in the 1927 Indianapolis 500. It was driven by Cliff Woodbury, owner of a Chicago service station, who qualified it 6th at 113 mph and finished 19th. Millers won the Indy 500 nine times and were so dominant that they made up 83% of the '500' grids from 1923 through 1928.

Around 12 or 13 rear-wheel-drive Miller 91 examples were originally built. Finding a correct motor proved to be a challenge, so the owner initially fitted the chassis with an Offy 220. A short time later, a rare Miller 91 engine became available. It was engine number 14, which had at one time been displayed as a standalone unit in a British museum. It was being offered by collector Robert Rubin of Southampton, New York.

This #15 Miller Boyle Valve Special was raced at the Indianapolis 500 in 1927. It draws from the basic designs originating from Harry A. Miller of Los Angeles, CA. The famous Miller cars won the Indianapolis 500 nine times. Miller cars accounted for 83% of the Indy 500 fields from 1923 through 1928.

This restored car features a 1.5 liter (91 cubic inches) straight 8 with dual overhead cam supercharged engine. This design by Leo Gossen in the Miller Factory is based on the 1912 Peugeot Grand Prix engine. The rest of the original drivetrain is a 3-speed transmission and a solid rear axle. This car qualified 6th at a speed of 113 mph by Cliff Woodbury, a Chicago service station owner, and finished 17th.

Miller cars like this example were also raced in the same trim, drive train, and tires on dirt ovals and high banked wood board tracks in Beverly Hills, CA; Fresno, CA; Altoona, PA; Woodbridge, NJ; and Pittsburgh, PA. All of these events were an integral part of the AAA National Championship for these cars.