The weird and wonderful cars of the ‘500,’ part 6

Published On May 3, 2016 » 5791 Views» By Marshall Pruett » Blogs, IMS, IMS History, Indy 500

We’re chronicling 100 days of Indy 500 history on #SpeedRead leading up to the historic 100th Running. With 26 days to go, racing journalist Marshall Pruett continues his look back at milestone cars and technology.

More Pruett: Weird and wonderful cars: Part 1Part 2, Part 3, Part 4, Part 5 The mighty “Offy” | Penske’s ’94 dominator | The “Fantastic” Turbine | Murphy’s Miller straight-8 | Yunick’s winged Watson More 100 days

We have fallen in love with the Indianapolis 500’s most accomplished designs since the Marmon Wasp won the first race in 1911. Since then, countless favorites have graced Victory Circle—Millers, Kurtis Krafts, Eagles, Penskes—and dozens of other race-winning cars or inspiring machines have enriched the great race.

And then, as history has recorded, we have the cars that reached too far or, in some cases, not far enough in pursuit of glory at the Indy 500. They stand as the weird and the wonderful, and some represent interesting footnotes—or origins—in chassis and engine design.

In Part 1Part 2, Part 3, Part 4 and Part 5 of this series, we’ve enjoyed looking back at cars that aren’t household names, yet have become beloved entries in Indy’s technological march to May’s 100th 500. We hope you enjoy Part 6.


1. 1938-46 Miller-Gulf Six

As far as ‘firsts’ go at the Indianapolis 500, Lee Oldfield’s primitive 1937 entry was the original rear-engine car to appear at the Speedway, but it lacked speed and development and failed to make the race.

Oddly enough, the first proper rear-engine car, the Miller-Gulf Six, also failed to qualify during its first appearance in 1938 with Ralph Hepburn at the controls. Like many pioneering cars that lapped the 2.5-mile oval, Miller’s rear-engine car needed more time to work out the kinks, and on its return in 1939 with George Bailey, its earned sixth on the starting grid.

What a stunning piece of machinery to behold.

Underwritten by the Gulf Oil Company, the rear-engine cars designed by Harry Miller raced for many years at the Brickyard, and as one might expect from Indy’s grand innovator, the futuristic Miller-Gulf Sixes evolved at a fantastic pace.

With its six-cylinder supercharged engine mounted behind the driver, Harry Miller’s chassis layout moved Indy’s conceptual goalposts beyond reach of the competition and, at least in the beginning, beyond his reach of qualifying for the race.

The extreme complexity—and weight—of the all-wheel drive system and the supercharging system added a significant amount of tonnage to the vehicle, which hampered its initial pace. Miller sought to optimize every aspect of his Six, which was a unique approach in 1938. Looking at some of the other cars from the era, each had something different, but Miller went to the extreme: Every aspect of the Six was taken to the outer reaches of the accepted norm.

The motor’s flywheel and clutch system faced the driver, rather than the back of the car. Its four-speed transmission, which one would have expected to see affixed to the rear, shared space with the front-mount radiator. All four corners of the Six utilized independent suspension—another break from tradition. The sizeable supercharger was housed at the back of the car instead of sitting close to the 180-cubic-inch inline-six motor.


The original full-length trumpet-style exhaust gave way to 1939’s glorious, individual art-deco exhausts; they look like something that sprang from a demonic church organ. The 1938 Six was an aerodynamic marvel, but the need to make more power to overcome its hefty disposition led to a large intercooler being fitted on the left side of the engine cover for the following year.

Teardrop fuel tanks rode on both sides of the car and were eventually built into its spaceframe chassis as it changed hands and was developed by new owners. Carburetor induction pipes were seen atop the rearmost bodywork in its final run in 1946.

The Miller-Gulf Sixes weren’t able to visit Victory Lane, but that shouldn’t diminish history’s view of their contribution to the Speedway. Set against the conventional Indy cars it faced (like Frank Wearne’s Shaw chassis, below), Miller’s Six won the inspiration war, foreshadowing the 1960s rear-engine revolution.

It was the first mind-bending package—the STP Turbine of its day—and continues to serve as one of the greatest technological leaps made at the Indy 500.



2. 1983 Rattlesnake-Cosworth

We left designer Roman Slobodynskyj and his 1981 Interscope “Batmobile” in Part 4, but he wasn’t done with Indy 500 designs. For 1983, and with far fewer resources at his disposal, the former AAR man penned the Rattlesnake chassis for journeyman driver Michael Chandler.


The Rattlesnake, which carried over some of the design cues from the Interscope, was among the final ‘independent’ cars to grace the Indy 500. Slobodynskyj’s aero treatment at the rear of the Rattlesnake continued what he started with the Interscope. With ducting to the radiator separated from the rest of the sidepod, the Rattlesnake fed the tall, elongated ground effects tunnels at just below the radiators and used contoured bodywork atop the rear—to the point of almost hiding the engine and engine cover—to meet with the upswept underwing profile.

The sheer height of the tunnels is given away by the Rattlesnake’s rear tires—they’re almost level with the Goodyears. Chandler overcame a poor starting position (30th) to place 16th after a gearbox problem forced his retirement on Lap 153.

3. 1947 Mercedes-Benz W154

A fascination with turning Grand Prix cars into Indy 500 specials was a common aspect of the great race through 1981 when the Williams FW07-derived Longhorn chassis made the final F1-to-Indy foray.

For the 1947 Indy 500, Duke Nalon reached back to 1939’s Mercedes-Benz W154 and went to great lengths to transform Rudolf Caracciola’s championship-winning car into a Speedway stunner.


The supercharged 183-cubic-inch V12-powered pride of Germany was fast enough the qualify mid-pack in 18th, and boasted impressive handling, but with an unfavorable power-to-weight ratio–and its relative age, the W154 was destined to become more of a footnote than a crossover Indy 500 champion.

Nalon placed 16th after dropping out with a burned piston and Chet Miller was credited with 20th on the W154’s farewell when another engine problem halted the Mercedes-Benz just past the halfway point in 1948.

4. 1981 Eagle Pepsi Challenger

The first thing to know about this car is Dan Gurney rates it as his favorite among all the cars All American Racers have produced. Coming from the Big Eagle, that’s high praise.

The Pepsi Challenger stood out from the other 32 entries with its arrow-shaped chassis and unfamiliar aerodynamics. And beneath its razor-thin engine cover, another strange solution could be found—a 351-cubic-inch, naturally-aspirated aluminum Chevy V8.

Mike Mosley was one of two drivers in the 1981 race to compete without a turbocharged engine which, on the surface, might sound like the wrong direction to follow, but in typical AAR fashion, the vehicle carrying that V8 is what made the difference.

Formula One-style ground effects tunnels were the rage in 1981. Teams used full-length sidepods to house long underwings that generated big downforce, but Gurney’s design team, led by John Ward and Trevor Harris, found another method to make that downforce while presenting a friendlier shape to the air.

Ward ditched the wide-mouth tunnels for brilliant vortex-generating devices AAR dubbed “BLAT” for “Boundary Layer Adhesion Theory,” that ran alongside the base of the cockpit (the piece directly below “Theodore Racing” in the photo below).

The BLAT pieces fed what’s best described as a half-underwing, and with the Pepsi Challenger’s matching upper bodywork that met the underwing at the back (the same practice found on the Rattlesnake chassis), AAR’s little arrow made the same kind of downforce without resorting to using large and conventional sidepods (Like Geoff Brabham’s March, below).


By getting rid a large percentage of the drag-producing bodywork that normally sat between the wheels, the Pepsi Challenger exploited major aerodynamic gains, and the power of the BLAT system was made clear by the relatively tiny front and rear wings. With the small floor footprint making most of this Eagle’s downforce, big topside wings were not required, which also improved the Eagle’s drag figures.

Mosley qualified an amazing second for the 1981 Indy 500 but was the first car out of the race with a broken radiator. The car’s potential resulted in numerous copies being built for customers to use in 1982 and 1983. Al Unser Jr. drove one to fifth place in his Indy 500 debut, but it carried a Cosworth turbo engine, just as all the Pepsi Challenger replicas used.

The 1981 car, like many of AAR’s designs, was met with considerable resistance by the sanctioning body, and thanks to Mosley’s impressive pace—and backroom politicking—its engine was soon banned and the car’s BLAT system was also outlawed by the end of 1983.

In an unexpected throwback to 1981, DeltaWing designer Ben Bowlby reached out to AAR while formulating his arrow-shaped Indy car concept and inquired about using the Pepsi Challenger’s BLAT.

IndyCar passed on Bowlby’s idea in favor of the Dallara DW12, and after the two visionaries spoke, the BLAT—and the new, sports car version of the DeltaWing—had come together as one in Gurney’s shop.

With Ward’s original BLAT blueprints at his disposal, and all of AAR’s composites and manufacturing capabilities engaged in producing the radical Le Mans-bound prototype, the Indy 500 had one heck of a story come full circle.

According to its critics—and the officials in charge of the rulebook—AAR’s 1981 Eagle was too creative to continue unaltered. Bowlby’s DeltaWing Indy car concept was also deemed to be a step too far and morphed into a sports car. Together, the Pepsi Challenger’s pioneering 1981 aerodynamics gave Bowlby’s DeltaWing everything it needed to fly on the Mulsanne Straights and corner with great speed 31 years later on its Le Mans debut.

How cool is that?



About The Author

Marshall Pruett

Marshall Pruett transitioned from more than 20 years as an open-wheel and sports car mechanic, engineer and team manager into his current role as a writer and reporter in 2006. Follow him @MarshallPruett []

Marshall, love these stories, especially the ones with the AAR Indycars and Roman Slobodynskyj's Indy creations. Have you considered Roman's Lightning-Offy laydown? Roman designed it for the Lindsey Hopkins team and Parsons Jr. drove it at Indy in '79 or '80. It was probably the last gasp for the turbo Offy.