By 1969, Porsche develops the 917 Spyder with a view to competing in the extremely popular North American racing series, the Canadian American Challenge Cup (Can-Am). Three units featuring 4.5-litre twelve-cylinder naturally aspirated engines are constructed in Zuffenhausen, and Jo Siffert takes one to the US to compete in the Can-Am races, ultimately placing fourth overall. The car becomes known as the 917 PA Spyder, with “PA” standing for “Porsche + Audi” as they are the two sales organisations in the US at the time.
Although the longtail 917 was introduced first, it was meant only for the Le Mans. This meant, the short tail 917 K ("Kurz" in German for short) was raced first. The only engine available in 1969 was the 4.5-litre flat 12. The factory team enters one 917 K also for the Nürburgring 1000 km race, where it scores 8th. The factory team would not enter 917 K for racing anymore in the season, only private teams will.
The 917 Kurzheck Coupé (917K) first appeared in 1970 and contributed more to the Porsche 917 story than any other variant. It was a high-down force version that featured a cut-off tail for increased downforce. This reduced the cars top speed, as much as 30 mph. Le Mans winner 1970, Interserie winner 1970 and Manufacturers' World Championship for Porsche in 1970.
The “shark fins” on the tail gave the Porsche 917 KH 1971 greater directional stability and reduced wind resistance by 11 percent. In 1971 a veritable armada of six Porsche 917s started at Le Mans. The car with start number 22 was special. The white race car with the characteristic Martini stripes had the new “shark fins” on the tail that Porsche had first used in pretraining in April. This 917 was also the first Porsche with a magnesium tubular frame to be used in a race.
For the 1969 racing season an absolutely new Porsche 917 with 4.5-litre 12-cylinder engine was created. Ferdinand Piëch relied on the skilfulness of Hans Mezger, who was responsible for the overall construction of the vehicle and its engine. The aim was to create the fastest racing car ever. Short and long tail versions were developed, called as the 917 K ("Kurz" = short in German) and the 917 LH ("Langheck" = long tail). The first car was assembled in December 1968.
With the aerodynamic instability of the 917 in the 1969, two separate configurations were used in 1970. These were the short-tail Kurzheck version and the less common Langheck or long-tail. Most of the 917's accolades were achieved by the 917 Kurzheck, leaving the Langheck a less popular, but ultimately just as potent contender.
Like the 917 LH of 1969 and 1970, the 1971 version was also made for one race only - the 24 hours of Le Mans. The 917 LH-70 had already proved that the body was excellent for Le Mans, so the aerodynamical modifications for 1971 were mild. The front was modified and the rear wheels were covered. The 917 LH-70 that scored 2nd at the 1970 Le Mans 24H (chassis 917-043) was modified for the Le Mans 1971.
The first turbo-Porsche, Can-Am winner 1972, Interserie winner 1972, 1973. The first ever publically seen turbocharged Porsche was the 917/10 Turbo with chassis number 917/10-011. It was entered for the June 11, 1972 Can-Am Mosport race. Mark Donohue was fastest in the qualification with it, but scored second in the 80 laps race after the 8.1-litre McLaren. The Porsche Turbo era had begun. Eight 917/10 were racing in 1972 in Can-Am and in Interserie.
Jo Siffert was the first to take the 917 to Can-Am championship. The car he used in 1969, was the 917 PA Spyder. Although he participated in one Can-Am race in 1970 with a 917 K, that season he skipped. He was back from mid-season 1971 and now with the 917/10. Only two 917/10 were created in 1971. The chassis 001 was used for testing and the 002 by Siffert. He took part in six races out of ten, managed podium finishes three times and scored 4th in the season, like in 1969.
The 1972 917/10 was similar in its design to the 908/03, but, of course, had the 12-cylinder engine instead of the 3-litre flat-8. The 917/10-72 was first seen at the Interserie Nürburgring race on April 3. It was the chassis 004 car of Leo Kinnunen and Keimola Racing Team AAW. Kinnunen scored 4th in the first race, but would win the championship by the end of the season. The second Interserie race was at Monza on May 1st and that race was won by chassis 917/10-002 and Willy Kauhsen.
An attempt to blend the best aerodynamic characteristics from both the short-tailed 917 K and long-tailed 917 LH led to the the 917/20, otherwise known as the Pink Pig. The car's combination of a long body, stubby face, and wide hips gave it a pig-like look, which inspired Porsche designer Anatole Lapine to give the car a pink paint job with butcher cut lines covering the exterior. It was hugely popular at the 1971 Le Mans race, and was the fastest in qualifying and nearly came in fifth place, before a brake failure caused it to crash before the finish line.
The 917/20 Turbo is a confusing car - its chassis number reads 917/30-001, but it is not the real 917/30. In its first race it was called as the 917/10 Turbo. Sharp eye can detect that it was not just the 917/10 Turbo, but an evolution of it. At the same time it was not the evolution of the 1971 Le Mans 917/20. Still, the car should not be called as the 917/30 to distinct it from the "real" 917/30 Can-Am racers and in 1974 it was decided to call it as the 917/20 Turbo.
The final evolution of the 917 was created after Ferdinand Piëch had left the Porsche company in 1972. Two complete 917/30 Can-Am cars with 2500 mm (98.4") wheelbase were made for Roger Penske Enterprises racing team. They were chassis 917/30-002 and 003. The 001 car was not a real 917/30 and was raced in Europe at the Interserie. The Can-Am 917/30 had a 5.4-litre flat 12-cylinder twin-turbo engine which produced so much power that nobody really knew how much.