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It is May, and to a vast throng of American motor sport enthusiasts the month of May means only one thing—Indianapolis, the hallowed Brickyard and the 500-mile race. The Indianapolis Motor Speedway proclaims itself as The Greatest Race Course in the World. While this contention is open to dispute, there is no denying the fact that over its 57-year history the Indianapolis 500 has become a rite, a tradition that is as American as apple pie. There is nothing that takes place at the Speedway during May that could not easily be accomplished in one busy week, but if it was, the 500 would be simply a race and not the great ritual spectacle that it is. What other race track in the World can draw 225,000 people to the course two weeks before the race to see one car at a time make its qualifying attempt? They return again, in smaller numbers, for the second qualifying weekend and then, on May 30th, a quarter of a million strong, they pack the place to the rafters. Indianapolis may not be the greatest race track in the World, or even the greatest race, but perhaps it is, as the Speedway radio, network annually proclaims, The Greatest Spectacle in Racing.

The big question mark this year, of course, is the performance of the gas turbine powered entries. Will they run away from the field, or is there still some life left in the venerable Offenhauser and its newer rival, the 4-cam Ford? It was only last year that Andy Granatelli began the turbine revolution when his STP Turbocar, driven by Parnelli Jones, came within 7½ miles of consigning the Fords and Offys to the scrap heap. Although the Turbocar hadn’t won, the last beer can had hardly been swept from the Speedway infield when the United States Auto Club began slapping restrictions on turbine cars in order to equate their performance with that of reciprocating engines. The most important of these rules changes reduced the permitted inlet area for turbines from 23.999 sq. in. to 15.999 sq. in.

Granatelli immediately cried foul and eventually took his case to court, where he sought an injunction against U.S.A.C. to restrain it from enforcing the new turbine rules. Last month a federal judge ruled that U.S.A.C. was entirely within its rights and Granatelli lost his case. The result was not unexpected, perhaps even by Granatelli. In February, before the case began, he had announced that in conjunction with Colin Chapman he was preparing six cars for this year’s race and that they would conform to the 1967 rules. Under cross-examination in court, however, he admitted that the Canadian-built Pratt & Whitney engine he was planning to use could conform to the 15.999 sq. in. inlet limitation. In the last week of March, after testimony had ended but before the judge had ruled in U.S.A.C.’s favour, the first of the new STP-Lotus turbines was unveiled at the Speedway.

The new car, which carries the Lotus designation Type 56, differs considerably from the original STP Turbocar. Its shape is a sharply accented wedge, with virtually flat top, bottom and sides. The monocoque chassis, constructed mainly of 16 s.w.g. aluminium alloy, is symmetrically located between the wheels with no suspension offset to counteract the left-turn-only Indianapolis oval. The cockpit is on the centre line of the car, with the engine in the rear (unlike the older car, which uses a side-by-side configuration for driver and engine and has a weight bias of 60% left, 40% right). Air inlets on the new car are flush NACA-type ducts just behind the driver’s shoulders, with the central exhaust about 12. in. behind his head. (Last year the STP Turbocar used a single NACA-type duct in the nose, but this has row been changed to a raised scoop.) The new car is also quite a bit bigger, having a wheelbase of 102 in. (compared with 96 in.), a track of 62.5 in. (60 in. on the older car) and an overall length of 14 ft. 2 in. (compared with 12 ft. 6 in.).

Both cars are using a modification of the Ferguson four-wheel-drive system but it is interesting that on the new one the drive from the engine output shaft to the transfer box is taken by a 3-in. Morse chain, instead of the geared coupling that was used last year. The older car suffered a number of gear problems in practice last year and was eventually eliminated when a bearing race in the transfer box failed.

Granatelli and Chapman originally planned to enter six cars for this year’s race, with Parnelli Jones driving last year’s model, Jim Clark, Graham Hill and A. N. Other in new STP-Lotus turbines, and two new cars in reserve. Since this is being written only a week after Clark’s tragic death at Hockenheim it is not yet known to what extent these plans will be altered.

The chief opposition to the STP-Lotus combine in the turbine field is expected to come from the Shelby cars co-sponsored by Goodyear and Carroll Shelby. These cars have been designed and built by Ken Wallis, and since he formerly worked for Granatelli it is not surprising that the Shelbys bear at least a superficial resemblance to the STP Turbocar. The General Electric T-58 gas turbines, their inlets reduced from 41 sq. in. to 15.92 sq. in., are positioned to the left of the driver’s cockpit and drive all four wheels through what Wallis calls a hybrid mechanical-hydraulic transmission system. He says this system differs significantly from most other four-wheel-drive transmissions by delivering power to each wheel on an individual basis. Such a system will obviously enhance the benefits of four-wheel-drive even further but the details of its operation are being kept carefully under wraps. Two of these cars will be driven by Bruce McLaren and Denny Hulme, with a third car in reserve. Both drivers have conducted tests with the car and Hulme, after driving the prototype in pouring rain, described it simply as “bloody fantastic.”

Yet another turbine-powered car has been entered by Jack Adams, who owns an aircraft sales business in Mississippi. The car has been designed by Glenn Bryant, professor in aero-physics at Mississippi State University, who has used his background to produce a body that is as aerodynamically clean as possible. The car is powered by an Allison 250 engine which has an inlet area of 12 sq. in.—quite a bit smaller than the General Electric unit used in the Shelbys or the Pratt & Whitney engine in the STP-Lotus cars. The engine drives all four wheels but Bryant is one of those who believes that fully independent suspension is not essential on the smooth Indianapolis oval. The Adams car has a de Dion rear suspension and a solid front axle suspended on coil springs. The car will be driven by Bob Hurt, who raced sports cars for many years but has concentrated on the U.S.A.C. circuit for the past two years.

But while the turbine-powered cars may steal the limelight, it still isn’t time to start writing obituaries for the reciprocating engines. Indeed, there will be a greater variety this year than there has been for a number of seasons. The redoubtable old Offenhauser, which was dethroned by Ford’s four-overhead-camshaft engine in 1965, has been making a comeback in the past 12 months in the form of a 2.8-litre version fitted with an exhaust-driven turbocharger. This engine is giving a reliable 625 h.p. and seems particularly suited to oval tracks, where there is less variation between minimum and maximum speed and the turbocharger is in almost continuous use. Of the three U.S.A.C. championship races that have been run at this writing, both those on oval tracks were won by cars with turbo-Offy engines while the one that was run on a road course went to a Ford-powered car. Ford, however, is not putting all its eggs in one basket. It, too, has developed a 2.8-litre turbocharged version of its 4.2–litre engine and while there were many initial teething troubles these are now reported to have been conquered. Present owners of 4.2-litre Fords can change them over to the turbocharged version with a conversion kit. Ford will also be represented in the third engine category permitted by U.S.A.C., which allows engines of 5-litre capacity if they are based on regular American production cylinder blocks. Dan Gurney is going this route and is using a 5-litre Ford fitted with his own Gurney-Weslake heads to power his second-generation Eagle. It is similar to the engine he used to win the last U.S.A.C. race of the 1967 season at the Riverside road course in California. Last but by no means least are the 4.2-litre four-overhead-camshaft Repco engines for Jack Brabham’s two entries, and one turbocharged, 6-cylinder Rambler engine.

With four different turbine-powered designs, six types of reciprocating engine, an even greater variety of chassis and the largest contingent of road racing drivers ever entered, this year’s Indianapolis 500 appears certain to be one of the most interesting for a long time.

D. G.

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