Editor's note: This story originally appeared in May 2011, one in a 10-part series on the history of the Indy 500
INDIANAPOLIS -- The popularity of the Indianapolis 500 arguably peaked in the 1960s, a decade marked by change throughout America as well as on the track at Indianapolis Motor Speedway.
While the nation became embroiled in the Vietnam War, a major philosophical battle broke out at IMS. From a humble beginning -- Jack Brabham's quiet ninth-place finish in the 1961 Indy 500 -- the rear-engine revolution consumed Indy car racing so quickly and completely that by 1967 there was not a single front-engine roadster in the 33-car Indianapolis field. Jim Hurtubise qualified his front-engine Mallard for the 1968 race and continued to enter front-engine cars at Indy through 1980, though they were never fast enough to make the show.
As is often the case in racing, the genesis for Indy's rear-engine revolution came from Formula 1, where Brabham won the 1959 and 1960 world championships in a Cooper powered by a 2.5-liter Climax engine.
Cooper lightly modified its F1 car and bored out the four-cylinder engine to 2.7 liters. Though down on power compared to the Offenhauser cars that comprised the rest of the field, the Cooper was considerably lighter and Brabham was able to take Indy's four 90-degree corners much faster than the roadsters, only to often be repassed on the long straights.
But the writing was on the wall, and Dan Gurney certainly noticed.
Gurney was racing full time in F1 in the early '60s, so he had firsthand knowledge of the superiority of rear-engine designs.
The versatile racer from California made his first Indianapolis start in 1962, driving a rear-engine car constructed by Mickey Thompson and powered by a Buick V-8 engine, and that experience was enough to convince him that a purpose-built rear-engine car would be highly competitive on a big oval like IMS.
So he approached Team Lotus founder Colin Chapman and the Ford Motor Company and convinced them to team up for an assault on the Indianapolis 500.
In October 1962, the Lotus F1 team traveled to Indianapolis, and Jim Clark lapped the Speedway at around 143 mph, just 3 mph slower than the slowest speeds in the Indy 500 field. This was significant because Clark's car was fitted with a 1.5-liter F1 engine that produced 175 horsepower, about half the output of the dominant Offys. The test convinced Lotus and Ford that they could be highly competitive at Indianapolis when on equal horsepower terms.
And so it proved. Clark qualified fifth and finished second in his Indianapolis debut in the 1963 500, with a Ford V-8 powered Lotus, beaten only by top star Parnelli Jones and his Watson roadster.
Ill will toward the rear-engine "funny cars" was already apparent; Jones' car appeared to be leaking oil, but was never black-flagged, leading some to conclude that USAC officials unfairly favored the American driver and car. Rival driver Eddie Sachs complained to that effect, claiming he crashed on Jones' oil, and Jones responded by slugging Sachs in the jaw!
Clark qualified on pole position for the 1964 race but retired early when his Lotus suffered a Dunlop tire failure. A year later, on Firestones and with an uprated Ford engine, Clark dominated the 500, leading 190 of 200 laps on the way to an easy win.
Twenty-seven of the 33 cars in the field featured rear-mounted engines, and the days of the roadster were clearly numbered. Perhaps as a result of the rear-engine revolution, USAC began experimenting with road racing, running a few events at tracks such as Indianapolis Raceway Park, Fuji Speedway in Japan, and Mosport and St. Jovite in Canada from 1965-68.
An even more radical technical solution showed up at the Speedway in 1967. STP boss Andy Granatelli commissioned a Paxton chassis powered by a Pratt & Whitney turbine engine normally used in helicopters. The strangely quiet machine was dubbed the "Whooshmobile," and after allegedly sandbagging in practice and qualifying, 1963 Indy winner Jones sped from sixth to first on the opening lap of the 500. Jones led 171 laps, but the turbine car ground to a halt with just three laps remaining when a $6 bearing failed.
USAC imposed restrictions to cut the power of the turbines, but a year later, Lotus produced a wedge-shaped chassis to house a turbine engine. Yet once again, defeat was snatched from the jaws of victory when Joe Leonard's Lotus turbine broke on a Lap 191 restart.
Although the turbines didn't dominate as Jones had dominated in 1967, USAC restricted the power plant even more and the turbines disappeared for good after a brief two-year appearance.
Meanwhile, the tired old Offenhauser got a new lease on life to compete with the Fords when turbocharged versions of the old four-banger appeared at Indianapolis in 1966, and Bobby Unser won the '68 race in an Eagle chassis built by Dan Gurney that utilized a turbo Offy.
By the end of the decade, the Ford V-8 was also being turbocharged and A.J. Foyt's pole speed topped 170 mph, an increase of more than 20 mph from 1960 qualifying speeds.
Aside from engine development, a tire war between Firestone and Goodyear also contributed to the escalating speeds. Goodyear entered Indy racing in 1964, and for the next 10 years, Goodyear and Firestone were unofficially the biggest-spending sponsors in the sport, contracting the top drivers of the era for huge amounts of money.
Foyt was without a doubt the driver of the decade at Indianapolis, scoring three of his four wins (1961, '64 and '67). In fact, the 1960s produced an amazing group of stars that would form the basis of Indy car racing for the next three decades. Jones made his last Indy start in 1967, but in his wake came a new generation of talent that included Mario Andretti and the Unser brothers -- Bobby and Al.
Foyt is the driver perhaps most synonymous with the Indianapolis 500.
He made a record 35 starts at the Speedway from 1958 to 1992, and he later became the race's first four-time winner with his victory in 1977. "Super Tex" also earned four Indy poles between 1965 and '75, led a record 13 races for a total of 555 laps, set career marks for laps completed and races led, and is the only driver to have won the 500 in front- and rear-engine cars.
Meanwhile, Andretti won the 500 in 1969 in his fifth start, and amazingly would never claim victory at Indy again.
Considered by many to be the most versatile racer of all time, Andretti finished third and claimed Rookie of the Year honors in 1965, and his 1969 win was made memorable by a sloppy kiss from car owner Granatelli in Victory Lane.
Andretti made 29 starts at Indy, the second-most in the history of the race, later finishing second in 1981 and '85. He scored pole position three times (1966, '67 and '87) and led the most laps in four of the 11 years he led the race. His 556 laps led at the Speedway ranks third on the all-time list.
As for Gurney, he never won the Indianapolis 500 as a driver, but cars designed and built by his California-based All American Racers team won the race in 1968 and '75 with Bobby Unser behind the wheel.
Driving his own Eagles, Gurney finished second at Indianapolis in 1968 and '69 and third in 1970, the year he retired from the cockpit, and he left a lasting impression on the sport with his legacy of technical innovation.
Those foreign funny cars were accompanied by a wave of international F1 drivers at Indianapolis. Clark was the most notable; the consummate gentleman racer concentrated on Formula 1, where he was a two-time world champion, but he also made five Indianapolis 500 starts from 1963 to 1967, leading four of those races and adding second-place finishes in 1963 and '66 to his 1965 victory.
Other F1 world champions who moonlighted at Indianapolis included Brabham, Jackie Stewart, Graham Hill (who won the 1966 race after Stewart dropped out late in the contest), Denis Hulme and Jochen Rindt.
Danger was still a constant factor at Indianapolis as five drivers perished during the 1960s at the Speedway, including Tony Bettenhausen, the patriarch of the famous racing family.
Rookie Dave MacDonald and the popular veteran Sachs were killed on the opening lap of the 1964 race; the fiery inferno prompted the switch from gasoline to methanol prior to the 1965 500. Chuck Rodee was killed during a qualification attempt in 1966, while rising F1 driver Mike Spence died behind the wheel of a Lotus turbine car while practicing in 1968.
The rapidly rising speeds and the constant element of danger were undoubtedly factors in the growth of the Indianapolis 500 in the 1960s.
With tickets for the race itself consistently sold out a year in advance, the four qualification days -- pole day in particular -- attracted huge crowds, with peak pole day crowds estimated at over 150,000. Twenty-five years into the Tony Hulman era, the Indianapolis Motor Speedway was still growing in popularity and could back up one of its many trademarked claims as "The Greatest Race Course in the World."