1970 Porsche 917 ‘Interserie Spyder’


1970 Porsche 917 ‘Interserie Spyder’

Of all the 917 variants, the ‘Interserie Spyder’ was one of the most successful. It won the Interserie championship outright for two years in a row before the model was replaced by the 917/10 of 1972. Three lightweight 917 Spyders were prepared by Porsche specifically for the Interserie, a new European-based racing series that mimicked the Can-Am rules from North America. Since it was initially run under Group 7 regulations, Porsche could remove the roof and make the design even more potent.

Under the spyder body was essentially the same design which won the 1970 24 Hours of Le Mans outright. This included the car’s lightweight aluminum space frame and the potent flat-12 engine in the rear. The Spyder bodywork was similar to a sole car made for the 1969 Can-Am that was called the 917PA.

Since the Interserie put a new lease on life for a number of cars which became redundant in the World Championship of Makes, the grids were diverse. Cars such as the Alfa 33, Ferrari 512M and Porsche 917 competed with new Group 7 designs from McLaren and March.

The first year in 1970 was a resounding victory for Porsche and the 917 Spyder with Jürgen Neuhaus taking two outright victories in six races. Not far behind was Gijs Van Lennep who placed second in the series with another 917. In 1971 Leo Kinnunen won the series with his 917 Spyder which was the beginning of his three year dominance driving for Porsche.

1970_Porsche_917InterserieSpyder1

In Detail

typeRacing Car
built atGerman
body stylistGerhard Schroeder
engineersHelmut Flegl, Paul Hensler
production3
engineAir Cooled 912.10 180º Flat-12 w/Dry Sump Lubrication
positionStressed Mid Longitudinal
aspirationNatural
block materialLight Metal w/Hard Chromed Cylinders
valvetrainGear Driven DOHC, 2 Valves per Cyl
fuel feedBosch Fuel Injection
displacement4494 cc / 274.24 in³
bore85 mm / 3.35 in
stroke66 mm / 2.60 in
compression10.5:1
engine designerHans Mezger
power432.51 kw / 580 bhp @ 8000 rpm
specific output129.06 bhp per litre
bhp/weight725.0 bhp per tonne
torque562.66 nm / 415 ft lbs @ 6400 rpm
body / framePolyester & Fiberglass Panels over Aluminum Spaceframe
driven wheelsRWD w/LSD
front tires4.75/11.30-15 Dunlop
rear tires6.0/13.50-15 Dunlop
front brakesInternally Vented Discs w/Dual-Circuit Calipers
rear brakesInternally Vented Discs w/Dual-Circuit Calipers
front wheelsF 38.10 x 22.86 cm / 15 x 12 in
rear wheelsR 38.10 x 30.48 cm / 15 x 12 in
steeringRack & Pinion
f suspensionArms w/Coil Springs, Bilstein Shocks
r suspensionArms w/Coil Springs, Bilstein Shocks
curb weight800 kg / 1764.00 lbs
wheelbase2300 mm / 90.55 in
front track1488 mm / 58.58 in
rear track1457 mm / 57.36 in
length4140 mm / 162.99 in
width1980 mm / 77.95 in
height920 mm / 36.22 in
transmission5-Speed Manual

Chassis

1970_Porsche_917InterserieSpyder1

Resurrected by the Porsche factory from one of three 1970 Le Mans cars entered by Gulf-JW Automotive. The chassis was nearly written off near the pitlane straight, but Porsche rebuilt the badly damaged hulk into a Spyder and restamped the chassis into 031. In this configuration it was campaigned by the German owner/driver Ernst Kraus and subsequently by Georg Loos’ Gelo Racing Team for well-known Porsche exponent Jurgen Barth.Later, the car became part of the Amalfitano collection in 1987 and was used at several high-end events.

Sources & Further Reading

Bamsey, Ian.Porsche 917 Kurz. Langheck. Spyder. Foulis & Co ltd, 1987.
Hinsdale, Peter.The Fabulous Porsche 917. Haessner Publishing, 1976.
Ludvigsen, Karl.Excellence Was Expected. Princeton Publishing Inc. Princeton, 1977.
Morgan, Peter.Porsche 917: The Winning Formula. Haynes, 1999.

Auction Sales History

1970_Porsche_917InterserieSpyder1

1972-73 Porsche 917 Interserie SpyderEx-Ernst Kraus/Jurgen Barth 1972-73 European Interserie and David Hobbs/Mike Hailwood Gulf-JW Automotive. Auction Source: Bonhams 2010 Exceptional Motorcars and Automobilia