The Miller 91 Supercharged Front Drive ‘Perfect Circle’ Indianapolis Racer

Miller 91 Perfect Circle

It’s neither official nor up for debate — Harold Arminius Miller is the greatest American race car designer of the 20th century. Born on December 9, 1875, to Jacob Miller and Martha Ann (Tuttle) Miller of Menomonie, Wisconsin, Harold (or just Harry) achieved renown in the 1920s and 1930s, thanks to his Indy 500 champions that won nine times, with the Miller engines propelling other cars to win the event 29 more times.

Back then, Millers dominated the Indianapolis grid, accounting for 83 percent of the racing machines at the field between 1923 and 1928. Harold launched his foray into the automotive industry with the short-lived Yale Automobile Company. He later moved to Lansing, Michigan, to work as a race mechanic for motoring pioneer Ransom E. Olds at Oldsmobile. There, he honed his mechanic skills during the early Vanderbilt cup races.

It is from here that Harold moved to Los Angeles, California, to open a small machine shop specializing in carburetor production. It wasn’t without merit that the preeminent automotive historian Griffith Borgeson called Harold “the greatest creative figure in the history of the American racing car.” Miller’s genius shone with what was perhaps the first bicycle-mounted engine and the first outboard motor.

Besides building a four-cylinder engine mounted on a boat, Miller gets credit to have produced the first aluminum pistons, the aluminum alloys still used in engine development today, and the first carburetors and induction system to use Helmholtz resonators. As a mechanic, Harold Miller’s racing voyage began with repairing and then building race cars. The man made a million dollars a year in the 1910s just from selling his trusty carburetors.

It was in the 1920s that Miller built his own 3.0-liter four-cylinder engine. Native American race car driver Jimmy Murphy won the 1921 French Grand Prix, propelled by Miller’s new engine. The engine, featuring dual overhead camshafts and four valves per cylinder, borrowed multiple engine designs that Miller had previously serviced in his shop, including Duesenberg and Peugeot engines. Murphy was the first to win with this engine, with Tommy Milton providing the financial backing to build it.

The Miller 91 Supercharged Front Drive Is An Ultra-Rare Classic Race Car

Miller 91 Race Car engine bay

Despite the FWD Miller 91 being super-expensive, Harold made at least ten examples of the FWD version, making 19 units in total, counting the – at least – nine RWD versions. We’re focusing on the “Perfect Circle” in this article, but the Miller 91s had different fancy names as they had detail differences, even though they’re essentially the same car in terms of design.

Harold loved the front drive (FWD) more because the setup allowed his race cars to be significantly lower, thanks to the absence of a driveshaft running under the driver to the rear axle. More so, Harold found that front-drive design improved cornering at high speeds, a capability that saw the models dominate the oval-tracked Indianapolis 500.

Notably, victory depends not just on the potent engine and FWD drivetrain but also on the driver’s weight and size since the car tucked a large fuel tank in its rear directly behind the driver, and the seat is just 18 inches wide. The 1.5-liter inline-eight got mounted backward on the front and mated to a three-speed manual transmission, sending power to the front differential.

The few surviving examples of the Miller 91 are now almost all in museums. You can check out one in the Smithsonian and another in the Indianapolis Motor Speedway Hall of Fame Museum. So, while you’re unlikely to see the model hit the market, a Miller 91 should set you back no less than $700,000 in the once-in-a-blue-moon that one shows up for sale.

The Miller 91 “Perfect Circle” Was Born To Win

Miller 91 Perfect Circle

Harold didn’t work alone. There was the self-taught automotive engineer and respected machinist Fred Offenhauser and the talented draftsman and mechanical engineer, Leo Goossen, working shoulder to shoulder with Harold to create some of the finest race-winning engines of the 1910s and 1920s. The Miller 1.5-liter engine is as intricate as, some say, a Swiss watch, thanks to Goossen’s impressive talent.

The engine’s maximum power output rose from 148 horsepower to exceed 247 horsepower at 8,000 rpm, allowing the mills to literally leave opponents in the dust. It was so hopelessly humiliating that the decision-makers had to adjust the rules twice just to give others a chance to at least make the top 10. The first such rule change was limiting the engine displacement to 1.5 liters in 1926, forcing Miller to develop a new inline-eight featuring a DOHC, hemispherical combustion chambers, a supercharger, and all alloy construction for low weight.

Besides the Indianapolis 500, Harold’s Miller race cars won 43 National Championships in total. Before his death in 1943, Harold partnered with the budding automotive designer Preston Tucker to develop an extraordinary automobile based on the Indy-winning race cars and intended for military use. They called it the Tucker Combat Car.

In August, this year, a 1927 Miller 91 Supercharged Front Drive “Perfect Circle” Indianapolis fetched $650,000 at an RM Sotheby’s auction at the Monterey Conference Center. The legendary Pete DePaolo bought it in 1927 and promptly won the 1927 AAA National Championship with it. Billy Arnold also drove the same car to win the Indy 500 in 1930 as well as the National Championship that same year, though modified to meet the new engine regulation via a Miller 122 engine. Indeed, a Miller is a winner

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