RACING CARS FROM THE SIXTIES
PORSCHE 917 (1969)
GERMAN
The Porsche 917 was undoubtedly the sensation of the 1969 season; most people expected Porsche to carryon with their Group 6 type 908 3 litre but in March 1969 they took the unusual step of announcing a new racing car at a motor show. They chose the Geneva Show for their announcement and immediately won the unofficial 'Car of the show' award given by the press. Porsche had decided to contest the Group 4 class as well as the Group 6 category, a collosal undertaking for a relatively small factory because under the rules for Group 4 at least 25 similar cars must be built before the FIA will homologate the car for International racing. But in April the necessary 25 cars were completed and standing ready in the factory yard for the FIA representatives to examine; Porsche even invited them to go for a drive in any one they liked but a quick examination showed that the cars were very much complete. The cars were given the O.K. for racing and Porsche were presented with the problem of finding 25 customers for their £14,000 racing car-not only 25 customers but also drivers who were capable of handling one of the most powerful racing cars in the world.
The 917 is built to Group 4 rules which require a maximum engine capacity of 5 litres, but' strangely enough Porsche did not take full ad vantage of this, for the flat-I2 engine was designed with a capacity of 4,494cc, over 500CC below the limit. The reason for this was that the designers had scaled up the flat-8 engine of the 908 Group 6 car which has a bore and stroke of 85mm x
66mm and a capacity of 2,997cc, so by adding four similar cylinders they arrived at the 4.5-litre capacity. The 917 engine is not the same as the 908 because it is improved in many details, actually giving more horse power per litre than its smaller brother. The flat-I2 air cooled engine has a magnesium crankcase split down the centre line, the crankshaft being divided in the centre at which point a train of gears drives outwards to the twin camshafts on each side of the engine. Two valves per cylinder are fitted and twin plugs per cylinder fired by twin distributors are also fitted. Bosch fuel injection, squirting downstream into the glassfibre injection trumpets, provides the fuel and on a 10.5 : I compression ratio the engine in its initial form developed 520bhp at 8,000rpm but development during 1969 yielded a claimed output of 585bhp which was a quite staggering figure if actually true. Like all Porsche engines the flat-I2 is air cooled, the horizontally mounted cooling fan being driven by a vertical shaft from the central train of gears. The power take off shaft is also driven from this gear train, the drive going via a three plate dry clutch to a five-speed all synchromesh gearbox and final drive unit with limited slip differen tial.
The chassis of the 917 is similar in concept-to that of the 908, being of the multi-tubular space frame type, but lightened by the use of a new aluminium alloy tubing. Suspension is also much the same as that of the 908 with double wishbones at the front and wishbones and radius rods at the rear, springing being by coil springs and Bilstein dampers. Disc brakes are fitted all round, the large ventilated discs being made by the German firm of ATE. The driving position is situated well forward, the coupe body being very similar to that of the 908. The car was designed with tail spoilers as an integral part of the body, the angle of the two individual flippers being changed by rods from the rear suspension. Magnesium wheels of I5 inch diameter and shod with Dunlop racing tyres are fitted and the fuel tank holds 30 gallons of fuel.
The first appearance of the 917 was at the Le Mans test day when a pair of cars appeared and Rolf Stommelen made the fastest practice lap in 3min 30.7sec over 3 seconds faster than the next car, a 3-litre Matra. The first racing appearance of the car was at the Spa 1000 Kms race but the first hints of trouble came during practice when the team drivers found that the cars were very unstable in a straight line and rather twitchy on the bends. It was decided to run only one car in the race for Mitter and Schutz but it did not last long before running into engine trouble. The Nurburgring 1000 Kms followed and a team of three 9I7’s was entered but none of the team drivers were keen to risk their necks in the powerful coupes on such a dangerous circuit and frantic phone calls were made to England to bring Frank Gardner and David Piper to handle one car, the others being withdrawn. They drove slowly and steadily and finished in eighth place.
Finally came Le Mans which Porsche wanted to win despite already having clinched the Championship. They entered a two-car team of 917’s to back up their four-car team of 908s and had sold the first 9I7 to go to a private owner to British driver John Woolfe. The cars were still handling poorly and Woolfe's co-driver Digby Martland decided it was too much for him and refused to drive, being replaced by Herbert Linge. A row developed over the eligibility of the rear spoilers of the 917s which were in theory banned by the CSI after the Monaco Grand Prix but the CSI decided to allow the cars to race with them as they would have been totally uncontrollable without them.
In the race John Woolfe's car crashed on the first lap, Woolfe being killed after swerving off the road, but the works 9I7’s led the race for much of the time until both began to suffer oil leaks, followed by clutch and gearbox problems which eliminated them from the race.
Two much modified 9I7s appeared in the Austrian GP and despite various bothers the car driven by Siffert and Ahrens scored the 9I7s first victory.
A much lightened open version was sent to the USA for Siffert to drive in the CanAm series but he had no success against the big 7-litre group 7 cars.
More Le Mans Cars from the 60ies onwards
Author: ArchitectPage
Length 15 ft 6 ins
wheelbase 7 ft 6 ins
front track 4 ft 8.5 ins
rear track 4 ft 9 ins
height 37 inches
