1969 917 The original from which all others would be spawned, even if it was the least successful of all. Developed off the back of the successful 908, the 4.5-litre 12-cylinder 917 was first run at Spa and the Nürburgring before heading to Le Mans. It suffered significant handling problems, mostly attributed to aerodynamic lift. The problem was so bad that all of the originals were modified, so none existed in their true configuration until Porsche restored chassis 001 for its 50th anniversary.

1969 917PA Spyder With the PA standing for Porsche + Audi as part of a marketing exercise, the roof was chopped from the chassis to create an open sports-prototype developed solely for use within the North American Can-Am championship. It featured a signature upwards flick of the rear bodywork to aid aero stability over the coupé. Jo Siffert was the driver of note, scoring a podium finish after switching to the new car mid-season.

1970 917KH Upset by the original 917’s wandering at high speeds, Porsche’s technical department conducted several days of testing with British engineer and team owner John Wyer at the Osterreichring, where the original design and the open-topped PA ran back-to-back. The cure was the upwards sweeping rear bodywork, known as the Kurzheck, or short-tail. The improvement was obvious from the start and the Kurzheck became the design of choice for all races barring Le Mans, even though Richard Attwood and Hans Herrmann ironically delivered the 917’s (and Porsche’s) first win at La Sarthe in short-tail format.

1970 917L While the short-tail improved the 917’s high-speed stability, the new rear added drag, therefore restricting its top speed. Not ideal at Le Mans in the 1970s, when the circuit was mostly straights. The solution was this Le Mans-specific Langheck, or long-tail, design. Even though it brought back some of the stability issues of the original, factory driver Vic Elford found it to be 25mph quicker down the straights than the short-tailed 917s and Ferrari 512s, and became the first man to lap with an average of above 240kph – at 242.685kph. Two were entered by the factory, with Elford’s suffering engine failure and the sister car finishing second, behind the more stable 917KH.

1971 917 16-Cylinder With the more powerful McLaren M8Fs and Lola T260s coming to the fore in Can-Am, Porsche was in danger of being left behind, so started coaxing more power from its engine. This chassis, 027, was used to evaluate a series of 16-pot units, scaling from 6 to 7.2 litres. On the dyno the 7.2 touched 850bhp, but was believed to be capable of 880bhp. The engine was fitted into a streamlined, lengthened and surgically ventilated chassis and driven by Mark Donohue for a few tests, including 56 laps of Weissach in September when Donohue believed up to 2000bhp would be achievable with turbos. Porsche then switched focus to turbocharging instead. The car never raced and only one example exists, fitted with the 6.6-litre flat-16 unit.

1971 917K While Porsche offered the option to use a bored-out 4.9-litre version of the flat 12 in 1970, the factory cars opted to stick with the proven 4.5-litre variant for Le Mans. For 1971 the larger unit was more proven and was even extended to 5 litres. The 917’s chassis changed, too, with ultra-light gas-pressured tubular magnesium framing being used in the winning chassis, 053 – the only coupé Porsche would race with that high-risk, rather flammable, combination. Vertical rear fins added more stability without extra drag. The car won Le Mans on the first attempt with Helmut Marko and Gijs van Lennep.

1971 917LH Based on the same principle of reducing drag, Porsche refined its long-tail design for 1971, with a redesigned frontal section, partial rear wheel enclosures and a single-piece rear spoiler assembly. Three cars were entered for pole and, despite Jackie Oliver securing pole in one, none finished the race and the long-tail project was finally scrapped.

1971 917 Interserie Spyder When Germany launched its own Can-Am variant in the form of the high-powered Interserie championship, Porsche had a natural base with the 917. Three cars were built; two were adapted from 917 PAs, while the third was developed from the 917K that had been crashed at Le Mans by Mike Hailwood. It won the Interserie title twice on the trot in the hands of Jürgen Neuhaus and Leo Kinnunen respectively.

1971 917/10 Built for Can-Am, the original 917/10 was more of a development mule for things to come than an out-and-out quest for domination. Jo Siffert drove the boxy first design to fourth in the points, as McLarens dominated. With the rules being similar to Interserie, a few 917/10s also dipped into the German class.

1971 917/20 Beautiful and playful, or just plain ugly… this is the 917 that divided opinion, with perhaps the most distinctive livery of all time. Created as a one-off to fuse the strengths of both the K and LH variants, the 917/20 emerged as a rather swollen, bulbous creation, with low-slung, wide bodywork. Designed by Anatole Lapine, it was decked in pink and marked up in butchery cuts; so the Pink Pig was born. Only lightly tested before Le Mans, it qualified seventh before being crashed by Reinhold Joest.

1972 917/10 Having been regulated out of the World Sports Car Championship – and as a result Le Mans, too – by the 3-litre limit, Porsche focused its efforts on Can-Am, and the search for power truly began. The second-generation 917/10 ran a 5-litre flat-12 engine with twin turbochargers giving up to 1000bhp. The bodywork was heavily sculpted at the front and a huge rear wing added to generate downforce. George Follmer won the Can-Am crown in its first year.

1973 917/30 And so we come to the 917’s apotheosis. For the final official variant of the 917, the engineers were essentially given free rein. The result was one of the most powerful sports cars ever. With all-new bodywork, a longer wheelbase and its engine bored out to 5.4-litres, the 917/30 was capable of nudging 1500bhp with the turbo taps wide open, but never raced with more than 1100bhp. It dominated Can-Am, to the point where America largely lost interest in its flagship sports car series.