This isn’t a discussion point: the sheer statistics can bludgeon you into submission. Porsche’s 956/962 series of prototype sports racers had a competitive lifespan at the highest level of racing for the best part of two decades and racked up more wins across the globe than any other racing car before or since.
17 classic endurance victories fell to the model, including seven at the Le Mans 24 Hours and six at Daytona. The double Le Mans-winning Joest New Man Porsche 956, chassis #117, won 23 times in a 52-race career over just three seasons: the most successful of a successful breed.
The car was at home everywhere, from the long straights and enormous speeds at Le Mans in Langheck mode to the bumps, twists and turns of American street tracks with short-tail, high downforce bodywork. It is still the fastest car to have lapped the Nordschleife: Stefan Bellof set a 6m11.13s lap in qualifying for the 1983 Nürburgring 1,000km (yes, imagine a battle armada of Group C cars racing at the ‘Ring).
The 956 immediately dominated from the moment it hit the track in 1982, as did its direct descendants the 962 and 962C from 1985. Third-party developments continued to stretch and morph the car into even more extreme forms, prolonging its life into the new – and far more hostile – decade of the ’90s.
Estimates vary due to damage and tub re-use, but well over 170 956s and 962 were built: over 120 by the factory (with 83 of those customer cars) and 56 known to have been built by specialist teams from kits or on their own tubs. The 956/962 achieved 39 wins in the World Sportscar Championship, 121 in Interseries and 55 in IMSA. The strange thing is how few times some of this enormous number of cars actually raced.
An example is the first ever chassis, 956/001. It raced just twice in 1982: second at Silverstone, won at Norisring. Retired to the Old Porsches Home. Similarly, the last ever works 962, /010, endured a challenging race at Le Mans in ’88 – and that was it. That means that a large number of the cars that survive are in incredible condition: as this Kremer Porsche 962CK6 from 1989 attests. In fact, often the cars have been raced more in the modern era than in period!
Two works versions of the 962 were developed: the straight 962 for the American IMSA series and the 962C for the international racing scene. Private teams introduced their own changes, and the fact that this 962CK6, chassis CK6/03, is virtually indistinguishable to the untrained eye from the 956 that rolled out of Weissach eight years earlier speaks volumes about the efficiency of the design.
Only minor differences stood the 1985-onwards 962 models apart from the 956 they replaced, and the foundation for all this success had been laid just three years earlier. Porsche’s American but German-born boss, Peter Schultz, wanted to take the firm into Indycar racing and specifically to the 1980 Indianapolis 500. A 2.65-litre twin-turbo engine had been developed, but a change in regulations counted out the single-seater move.
Back in the sportscar division, the plan had been to campaign the street-derived 924 Carrera GTR the following year – but Schultz wanted more than just a class win. The venerable Group 6 936 open-top sportscar was literally wheeled out of the Porsche Museum and into the race workshop, where the Indycar engine was installed. The car won the 1981 Le Mans 24 Hours in the hands of Jacky Ickx and Derek Bell – the engine had proved itself, now it just needed a home.
This happily coincided with the announcement by the FIA of the new Group C rules, and it occurred to Porsche that they had the ideal engine sitting about awaiting a new role. The rules dictated only a weight limit (800kgs initially) and a fuel restriction of 60 litres per 100km. That was it. Success in Group C would be a trade-off between finding the right chassis and engine to deliver speed but efficiency. Anything could be right, and everything took part, from four to 12-cylinder cars. It was an engineer’s formula and a designer’s dream – perfect Porsche territory. Norbert Singer, Klaus Bischof and Peter Falk headed up a new Porsche special racing projects team, and were the architects of the inexorable rise the 956/962.
The car had just a nine-month gestation from sign-off to turning a wheel in anger, though they weren’t alone in that because of the late delivery of the complete rules package. Manufacturers had to second-guess what the new Group C rules would and wouldn’t include (a ridiculous situation that continues even now in F1 and sportscar racing): BMW guessed wrong and pulled the plug on their programme when the full package was revealed; Lola had to completely redesign its T600.
The 956 was sketched out after the 1981 Le Mans race, and with six months until the 1982 edition the first car still wasn’t built. With three months to go it still hadn’t run – but just six weeks after the first cars had been completed they raced for the first time at the Silverstone 1,000km and won. Six hours without missing a beat. The scene was set for the 1980s. So much for an end to Porsche dominance in sportscars.
The concept of the car was only slightly modified by the factory across the ’80s. The 962 was quite a simple update, a box-tick for IMSA rules that involved extending the wheelbase by a mere 4.8 inches to bring drivers’ feet back behind the front axle line, and in IMSA spec the twin-turbo was replaced with a single KKK unit: US race tracks were bumpier and shorter, putting torque at a premium.
The 962C was the Group C version, often run in low-downforce configuration and sticking with smaller twin turbos, which made it easier to drive on longer tracks and had less spiky power delivery.
Underneath, the 962 chassis continued to use a sheet aluminium tub: the 956 had been Porsche’s first all-monocoque design after decades of spaceframe chassis. It wasn’t a new concept by any means – even Jaguar’s 1954 D-Type was semi-monocoque – but Porsche had doggedly stuck with spaceframe even up to the 936 Group 6 car, which was still winning when it was five years old. But this method would neither stand up to new FIA crash tests for Group C or, more pertinently, be easily adapted to the more advanced aero that would be used. Porsche’s only previous experience with monocoque had been a decade before in CanAm, so they faced a steep learning curve.
For the 956 the engineers had decided to not risk using the new honeycomb or carbon materials that were starting to emerge from the aerospace industry and leech into Formula 1, and in fact the factory would never go down that route even with the 962 revisions, leaving it to third-party fabricators. An aluminium alloy rollcage protected the cockpit and a tubular structure supported the flat-six engine, which would not be a stressed member.
Safety was a side concern at the time, not written in stone into the rules. Crash structures were defined in volume but not content, so were soon filled with radiators and ancillaries. The fuel-cell was mounted between the nose and cockpit.
The 962 was a full ground effect car: the technology was already being use in F1, but required a lot of adaption and complexity to make work in the context of a comparatively big sportscar. Skirts couldn’t be used to seal the undersides like in F1 because of the two-seater monocoque design and sidepod requirements, so there was initially a lot of trial and error in the wind tunnel. As has already been mentioned though, what was produced in 1982 continued in basic form until ’89. Porsche tend to get these kind of things right.
The power and reliability of the flat-six boxer engine might not have been in question, but its packaging was: the shape of the unit got in the way of the ground effect tunnels and venturis. But the engine stayed. Budget constraints meant that the money simply wasn’t there to design a new chassis plus an engine as well, and once the challenges had been overcome the only thing that changed over the years was the engine capacity. For the 962 a new three-litre unit was installed: the six-cylinder unit used four valves per cylinder, with air-cooled cylinders and water-cooled cylinder heads.
Driving these cars was a very different experience for those at the beginning of the ’80s compared to the end. In the early decade ground effect was rare outside F1, and the downforce took some getting used to. Speeds had to be up to get the aero working efficiently, and it was physically hard work with unassisted steering and steel brakes.
But the 956/962s were also known to be very forgiving, which is why they became such successful cars in the hands of amateur drivers as well as the seasoned pros, despite some neutral understeer from the spool diff locking the back axle.
The cars were built not just to be fast, but fast for 24 hours. Although the suspension components seem pencil-thin in isolation, together they presented a strong front to the rigours of 24 hour races. At the front were asymmetrical wishbones, with titanium rising-rate coil springs over Bilstein gas dampers.
At the rear, lower wishbones with parallel upper links, and agains titanium coils over Bilstein dampers.
The synchronised five-speed gearbox was the workhorse of the 962C: Porsche’s PDK twin-clutch semi-automatic preselector ‘box was tried on and off, but it had a troubled development and most teams preferred to stay with the bulletproof simplicity of the five-speed.
Kremer’s 962CK6 weighed in at the regulation base of 850kg, was 4,770mm long and had a wheelbase of 2,770mm – 120mm longer than 956). CK6/03 originally raced at Le Mans with BBS multi-spoked rears and the smaller fronts mounting ventilated covers: 16″ rims with 12×16 at the front and 15×16 at the rear. It now sits on very fetching Volk Racing rims, which the #11 sister car raced on that year.
Although the 962C and CK6 looked virtually the same from the outside as the 956, the car had got progressively faster, which was mostly down to engine improvements. Power increased from around 650hp in the early 956s to as much as 850hp in the late 962s, and fuel efficiency also went up, thanks to improvements with the Bosch electronics and Motronics engine management system.
