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16 Apr 2019

Apex Predator – 917 at 50: Part 1

Marking the 50th anniversary of the 917, we revisit the ultimate incarnation of Porsche’s most significant racer

The 12th March 1969 was a defining moment in Porsche’s history. On this day, some fifty years ago, the very first 917 was unveiled at the Geneva Motor Show. Before a global audience of press and public, Porsche had announced its intention to enter a new era of sportscar racing, and announced its desire to win big.
The 917 programme ran from the Spring of 1969 until late 1973, eventually dominating top tier motorsport on two continents and cementing Porsche’s global racing reputation. From a faltering start to the overwhelming success of the Can-Am car featured here, the 917 remains one of the most evocative, iconic sports cars of all time.
It was created in a remarkably short timeframe, evolving the smaller 908 to take advantage of new regulations implemented by the FIA on the International Championship of Makes for the 1969 season. With maximum engine capacity set at 5.0-litres and the minimum homologation requirement reduced to 25 cars, Porsche had spied a window of opportunity to achieve its ultimate sporting goal: outright victory at Le Mans.

Under the auspices of Ferdinand Piech, chief engineer Hans Mezger began work on the 917 in 1968, conceiving an ultra-lightweight, TIG-welded aluminium tubular spaceframe. Mezger was also responsible for the powertrain, a 4.5-litre 180 degree air-cooled flat-twelve mated to a longitudinal four-speed transmission. The car would be clothed in a thin skin of fibreglass, its elegant contours shaped in Weissach’s nascent wind-tunnel.
Early testing found the light and powerful 917 to be hugely unstable, suffering severe chassis distortion and rear end lift, with the driver sat alarmingly far forward in a highly fragile structure, hemmed in by two vast, flexing fuel tanks.
Luckily, some early intervention from John Wyer Automotive, onboard to campaign the car with full factory support, accelerated the introduction of the ‘Kurzheck’ or short-tail bodywork. This dramatically stabilized the car for the 1970 season, culminating in that famous maiden win for Porsche at Le Mans.

For many motorsport fans of a certain age, the 917 perfectly encapsulates that golden era of sportscar racing. The memory of Pedro Rodriguez slithering around a submerged Brands Hatch during the BOAC 1000KM in 1971 is a common thread among PCGB members and probably for many the reason they caught the Porsche bug in the first place. The drivers’ stories are plentiful and eye-popping too, from 200mph slides to the flat-out runs down Mulsanne in the dark, without even lifting for the kink. This was a car that made heroes of its drivers and of itself. A fearsome, beautiful, winner – everything that a thoroughbred racer wants and needs to be.
The 917 swept all before it in 1971, again winning Le Mans outright in the be-finned Martini Kurzheck driven by Gijs van Lennep and Helmut Marko. But across the Atlantic, where the 917 was running in the Can-Am Championship, it was a different story. Here, the air-cooled flat-twelve was struggling against the experience and sheer power of the dominant V8 McLarens.
Porsche hatched a plan, recruiting Can-Am veteran Roger Penske to help develop the car for this unrestricted and largely unfamiliar series. The 1972 917/10 would be turbocharged, its output ranging from 840 to over 1000bhp. And combined with an increase in downforce from revised bodywork, the new 917/10 unseated McLaren in grand fashion, winning six of nine rounds.

Porsche was far from finished, however. Having worked intensively with Penske and lead driver Mark Donohue in the off season, it then built a short run of what became the ultimate evolution of the series: the 917/30.
Displacing 5400cc, the 917/30 used Bosh mechanical fuel injection and huge twin KKK turbochargers. In order to improve stability, the wheelbase grew to 2.5 metres, some 190mm longer than the 917/10. The flimsy fibreglass bodywork was also extended front and rear to increase downforce. The car weighed just 850kg dry, of which about a third of that was engine.
In these early days of forced induction, lag from the turbos was of the biblical variety, with power coming in so suddenly that many regarded the 917/30 as undriveable. Porsche equipped Donohue with a cockpit boost controller to regulate the car’s manifold pressure. This had the dual benefit of sparing the engine and saving fuel, for the 917/30 was so thirsty that it needed 440-litres of fuel in two vast tanks.

The 1973 Can-Am Championship was an absolute whitewash. Donohue won six of the eight rounds, amassing 139 points against the next-best’s 62. But Porsche’s obliteration of the competition prompted an SCCA rule change for Group 7 that strictly limited fuel consumption, hobbling the 917 at the peak of its power.
The car was to enjoy one final flourish, however, when Porsche took on a world record attempt for average speed on a closed course. On August 9, 1975, the 917/30 turned out onto the 2.6-mile Talladega Superspeedway in Alabama, sporting new charge-air coolers that enabled a continuous output of 1,230bhp. At the wheel once more was the apparently fearless Mark Donohue, who average 221.12mph and a straight-line speed of over 240mph. The record stood for 11 years.

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