Darin Schnabel ©2015, courtesy of RM Sotheby’s
The Miller 91 was a true tour de force of rear-wheel-drive racing technology. It was so successful and its domination on speedways of the 1920s was so complete that it was effectively responsible for its own demise. The AAA’s rule change for 1930 to the “Junk Formula” was, in fact, adopted to stop the Miller 91’s seemingly unstoppable winning streak. When the rule change that limited displacement to 1½ liters (91 cubic inches) was announced for the 1926 racing season, Harry Miller could have merely shortened the stroke of his nearly unbeatable 122-cubic inch engine and continued producing and selling the rear-drive race car that he first introduced in 1923. Instead, in typical fashion, Miller’s staff of extraordinarily talented men was assigned to design and build an entirely new car. All of the new 91-cubic-inch engines were supercharged, and at introduction, they developed 155 horsepower at 7,000 rpm. Extensive on-track development work resulted in refinements that eventually boosted output to well over 250 horsepower at 8,000 rpm. The consigned car was repainted as the Boyle Valve Special when it wore #15. It started 6th on the grid at the 1927 Indianapolis 500 and finished a respectable 19th. The original Boyle Valve Special’s cosmetic livery was precisely copied on this car based on the drawings of famed automotive artist Peter Helck, with the triangular logo complementing a deep finish of white and light blue paintwork.  

SCM Analysis


Vehicle:1927 Miller 91
Years Produced:1926–29
Number Produced:12 or 13
Original List Price:$10,000
SCM Valuation:$700,000–$800,000
Tune Up Cost:$1,500
Chassis Number Location:On frame rail
Engine Number Location:Brass plaque on block
Club Info:Antique Auto Club of America
Alternatives:Cooper Miller racer, Duesenberg 91 racer, Miller Detroit racer
Investment Grade:B

This car, Lot 153, sold for $770,000, including buyer’s premium, at RM’s Amelia Island sale in Amelia Island, FL, on March 14, 2015.

A driving force

Harry Arminius Miller was a major factor in the history of early racing in this country. No — it’s better stated that he was the major factor.

Like many innovators of the era, Miller received limited formal education. But his mechanical aptitude and inquisitive mind resulted in numerous significant inventions. He received his first of numerous patents in 1905 for a “sparking device,” which he sold to the Peerless Motor Car company. In 1909 he received his first patent for a carburetor, and many more for that device quickly followed.

In 1911, he formed New-Miller Manufacturing, which made carburetors into the early 1920s. Then, in 1912, he formed Master Carburetor Co. This, in turn, led to the Harry A. Miller Manufacturing Company, for which he manufactured fuel pumps, carburetors and pistons made from Alloyanum — his formula for aluminum. By 1915, Miller was building his own engines and chassis for race cars. His shop superintendent was Fred Offenhauser, who Miller later placed in charge of the engine and race car department.

The 183, 122 and 91

The first Miller Eight — the 183 — was funded by a $5,000 deposit placed by Barney Oldfield. Oldfield had borrowed the money from Henry Ford. The engine became the basis for every successful Miller, Offy, Meyer-Drake and Drake racing engine built until 1978.

Miller’s 183-powered cars dominated the 1922 American season. The 183-ci formula, however, expired in 1922. A new two-liter (or 122-ci) formula resulted in Miller producing an improved motor with a stronger five-main-bearing lower end and an available bolt-on supercharger, which boosted speed considerably. It was a simple but elegant design, placed into a slim single-seat race chassis and body. Miller’s cars continued to dominate, and the only major race they did not win in 1923 and 1924 was the 1924 Indy 500.

In 1926, the Indianapolis Speedway management decided to follow the international sanctioning bodies and reduced its allowed engine size to 91½ cubic inches. The new Miller 91, developed for the rule and produced until 1929, was similar to the 122, but was supercharged from the beginning, with a centrifugal unit running off the rear of the crankshaft. It was light, efficient and available as both rear- and front-wheel drive. Again, Millers became nearly unbeatable, setting new records — Leon Duray’s 124-mph lap in a Miller at Indy in 1928 stood as the record for nine years.

Umbrella Mike’s racer

These cars were very expensive when they were built, costing upwards of $10,000 each. That brings us to the other personality related to the Miller 91 “Boyle Valve” Special — car owner Michael J. Boyle. He was the tough boss of the Chicago local chapter of the International Brotherhood of Electrical Workers. He was called “Umbrella Mike,” as he was seldom without one when making his rounds. Extended in the air was a signal for his men to strike; while hanging partially open on the edge of his desk or bar, it became the receptacle for tangible enticements for his favor. While active in the underbelly of Chicago, he was also a major patron of American championship racing.

Boyle’s cars wore the logo of one of his businesses — a company that manufactured automotive valves. They made a replacement valve that seated flat rather than in a conical seat. Interestingly enough, the design was not practical for racing engines, and not even Boyle’s own crew used them.

Boyle, who started racing in 1926, won three Indianapolis 500s and fielded three- and four-car teams, winning the 1940 Indy 500 with Wilbur Shaw at the wheel.

Piece of history or collection of parts?

The Miller Special presented by RM was based on one of two Miller 91 front-drives that Boyle purchased from Harry Haartz in 1926. One, the Number 15, was driven by Cliff Woodbury. That car tied course records at Altoona and Culver City during the 1927 season but could finish no higher than 19th at the Indianapolis 500, as Woodbury blew his supercharger on the 108th lap.

Only 12 or 13 Miller rear-drive 91s were originally built, which explains why parts are impossible to find today.

This car was built from a Miller chassis with a correct Miller 91 engine that had once been displayed in a British museum. It also has a correct gearbox — which is extremely rare — and an original rear end. The aluminum body was built during restoration, based on an original set of Harry Miller blueprints for the Miller 91, and it was finished in the striking livery of the Boyle Valve Special.

At first glance, it would appear that the buyer of this Miller 91 paid three quarters of a million dollars for a bunch of assembled parts. On reflection, however, we are looking at a race car; engines were changed with regularity and bodies got smacked around in the course of business. There are, however, a few original no-stories Millers out there, and as we saw when a 122 brought over $2m at RM’s sale of the Joe MacPherson Collection in June 2008 (ACC# 117191), prices for them can easily crest the seven-figure mark.

Harry Miller had a 60-year involvement with the Indianapolis 500, and this Miller 91, with correct engine, gearbox and drivetrain, is an irreplaceable part of that history. It may not be all-original, but from where I sit, the price paid certainly seems most reasonable.

(Introductory description courtesy of RM Auctions.

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