Guide: Porsche 917 / 69 Spyder
Background
The USA was overwhelmingly Porsche’s largest export market and, although the World Sportscar Championship visited three times a year (Daytona, Sebring and Watkins Glen), most American fans preferred to watch shorter races for spectacular unlimited machinery.
The unlimited class was called Group 7 and imposed practically no restrictions on designers.
By contrast, the 1969 World Sportscar Championship was organised for Group 6 Prototypes (three-litre engine limit) and Group 4 Sports cars (five-litre engine limit with a 25-car production requirement). Vehicles from both categories notionally had to be road legal with a full complement of lighting and a spare wheel.
Since its inception in 1966, the Canadian-American Challenge Cup (Can-Am) had established itself as the premier international arena for Group 7 racing.
Each event was typically held over a distance of around 200 miles and an enormous prize fund attracted many of the top F1 drivers. Can-Am races were originally held between September and November.
For 1969, the Can-Am Championship was expanded from six to eleven rounds. The first event took place in June and the last was in November: it was predicted to be the biggest and best series yet.
Although the 917 and 908 programmes had utterly decimated Porsche’s competition budget, their American partners wanted to contest the 1969 Can-Am season. To get their hands on a suitable machine, Porsche+Audi North America, Volkswagen North America and the West Coast Porsche and VW distributor, John von Neumann, financed the creation of a 917-based Group 7 Spyder.
Authorised at the beginning of June 1969, the new 917 Spyder evolved over the next ten weeks and was referred to as the 917 PA (Prototype America).
Chassis
A pair of new 917 aluminium spaceframes were fabricated for the job.
Chassis 027 was retained by Porsche for development work and chassis 028 was sent out to race in the USA.
As removing the roof reduced stiffness, extra tubes were added (including new rollover protection for the driver). Otherwise, the complex and super lightweight aluminium-tubed spaceframe was largely identical to the standard 917.
The wheelbase was unchanged at 2300mm.
Independent double wishbone suspension with coil springs and Bilstein dampers was fully adjustable.
All manner of of exotic alloys were used; magnesium and titanium were particularly prevalent on the 917 Spyder as there was no minimum weight limit in Group 7.
Brakes were ventilated discs with ATE calipers.
Goodyear produced special tyres for the wider centre-lock five spoke magnesium alloy wheels. A 15-inch diameter was retained but widths were increased from 9 to 10.5-inches at the front and from 12 to 15 or even 17-inches at the back.
The rocker panel fuel tanks were enlarged to 190-litres and, when brimmed for a 200 mile race, negated any weight saving.
Bodywork
Bodywork was clearly derived from the 908/02 Flunder that had made its debut on June 1st 1969 at the Nurburgring 1000km.
With its smooth profile, the 917 Spyder was initially unencumbered by aerodynamic flaps and spoilers.
The most radical difference to any previous Porsche Spyder was at the back where the entire rear bodywork was cut away behind and up to the top of the wheels.
The rear deck was extended by around a foot above and behind the rear wheels and a spoiler was fitted along the trailing edge.
Although created with nothing more than weight saving in mind, a few weeks later, Porsche discovered this new tail section solved practically all the Group 4 917’s stability foibles.
Engine & Gearbox
For the engine, Porsche’s most powerful incarnation of the Hans Mezger-designed 180° Flat 12 was installed: it was the same 580bhp version used in the pole-starting 917 driven at Le Mans by Rolf Stommelen and Kurt Ahrens Jr.
The air-cooled type 912/00 motor was effectively a combination of two Porsche 2.25-litre Flat 6 engines.
Its crankshaft (divided in the middle) rested on plain bearings with titanium connecting rods while, at the centre of the engine, a train of gears drove four camshafts operating two valves per cylinder and the vertical shaft for the 917’s distinctive horizontally-mounted air-cooling fan.
The 912/00 engine used a magnesium alloy block, aluminium alloy heads and displaced 4494cc thanks to a bore and stroke of 85mm and 66mm respectively.
However, until turbocharging came on stream, Can-Am was all about engine size and, compared to its Group 7 rivals, the 917 Spyder was giving away around 2500cc.
As usual, mechanical Bosch fuel-injection was installed along with two separate ignition distributors that fed the 24 spark plugs.
Compression was set at 10.5:1.
Since launch, Mezger’s engine had gone from 520bhp at 8000rpm to 580bhp at 8500rpm.
The longitudinally mounted all-synchromesh gearbox was designed to take four or five gears but only four speeds were used in the Spyder.
Weight / Performance
In its completed state, the new car weighed 775kg which was 125kg less than the Coupe.
0-62mph took around 2.5 second and top speed would have been about 190mph.
Production & Testing
Both Spyders were finished in early August. They were then given a brief shake down at Porsche’s Weissach proving ground.
Chassis 027 stayed in Germany for further development while 028 was flown out to the USA.
028 would be campaigned under the Porsche+Audi banner.
Jo Siffert (paid by Porsche) would do the racing.
The American operation was overseen by Richie Ginther.
1969 Can-Am Championship
Porsche missed the first four rounds of the 1969 Can-Am Championship. On each occasion, victory went to the works Gulf-backed and Chevrolet-powered McLaren M8Bs. McLaren drivers Denny Hulme and Bruce McLaren had scored a brace of victories each.
1969 Mid-Ohio Can-Am
The first appearance for the 917 Spyder was round five at Mid-Ohio on August 17th. Chassis 028 was presented in white with a blue V-shaped stripe plus discrete Porsche+Audi branding.
Front winglets plus a chin spoiler had been added to the nose and a horizontal bank of vents had been cut from the backs of the sills.
Siffert qualified the new car seventh and rose to finish fourth in the race, but the Swiss had found traffic a problem on the narrow 2.4-mile track.
Denny Hulme won from Bruce McLaren in the works M8Bs. Chris Amon finished third in his Ferrari 612 P.
1969 Road America Can-Am
Two weeks later, the Can-Am circus rumbled 500 miles north west to Wisconsin for round six at Road America (August 31st).
Vents had been added in the front wings to reduce air pressure but Siffert was still not happy with the handling and started eighth.
His race ended on lap six with a blown engine after he missed a gear.
The works McLarens once again dominated. Having locked out the front row in qualifying, Bruce McLaren took the win from Denny Hulme. Chuck Parsons finished third in the Carl Haas-entered Lola T163.
1969 Bridgehampton Can-Am
The picturesque Bridgehampton circuit in New York state hosted round seven on September 14th.
Chassis 028 arrived with new rear wing flaps and a fresh engine after the blow up at Road America.
Although Siffert was not making much progress in terms of grid positions (he was again seventh quickest), good reliability and a steady pace saw the Porsche+Audi team take their first podium in Can-Am racing.
However, no-one had yet managed to dislodge the works McLarens; Denny Hulme took the win from Bruce McLaren on this occasion.
1969 Michigan Can-Am
Round eight of the championship was at Michigan on September 28th and, to counter the Porsche’s front-end lightness around corners, even bigger front winglets were tacked on.
Siffert qualified a season best third for the race but McLaren had brought along three works M8Bs and gave a demonstration of just how far ahead they were.
As usual, Bruce McLaren and Denny Hulme made it a McLaren one-two.
It was the third works car, on hand for Dan Gurney, that really taught Porsche a lesson. Gurney hadn’t posted a time in practice so started from the back. He proceeded to lap Siffert’s Porsche which was admittedly trailing smoke from a minor seal leaking oil onto the exhaust.
Siffert eventually finished a creditable fourth but Porsche knew they would need a different kind of engine to win in Can-Am.
1969 Zeltweg Tests
Back in Europe, a test session was organised for early October at Zeltweg. Porsche were there with John Wyer Automotive Engineering (JWAE) who would manage the 917’s attack on the 1970 and 1971 World Sportscar Championship.
The factory took a short tail 917 Coupe plus their own Spyder (027) as JWAE wanted to put the aerodynamics of both cars under scrutiny.
The Coupe and Spyder shared an almost identical chassis, equally powerful engines and the same drivers so, when the Spyder started to post lap times around four seconds faster than the Coupe, it seemed obvious the fixed head’s problems lay with its bodywork.
As a result, the Group 7 Spyder-type tail was refined and adopted for the subsequent 917 K.
1969 Laguna Seca Can-Am
Back in the USA, three Can-Am races remained.
The first was at Laguna Seca on October 12th (round nine).
Siffert’s Porsche arrived with enlarged outlets atop each front wing and a new radiator exhaust vent cut into the detachable front lid. Big winglets were used in practice and Siffert qualified sixth.
Unfortunately, when Dan Gurney’s McLaren misjudged a pass in the race, he biffed the Porsche and knocked one of its winglets off. This forced a pit stop for the Porsche for the other winglet to be removed.
Now suffering from understeer, Siffert salvaged fifth and finished a lap behind the lead four cars.
Once again it was a works McLaren benefit as Bruce McLaren won and Denny Hulme was second. They were followed by the Carl Haas Lola T163 driven by Chuck Parsons and a Holman Moody-entered McLaren M6B for Mario Andretti.
1969 Riverside Can-Am
After the experience at Laguna Seca, chassis 028 arrived at Riverside two weeks later with a new full width fibreglass cover for the nose. Not pretty but definitely effective, it was enhanced with winglets and additional fins over the weekend.
Despite the upgrades, Siffert had his worst qualifying session of the season and posted eleventh quickest time; an oil leak had proved impossible to get at in time.
The problem then gradually worsened in the race and Siffert was black flagged at quarter distance with excessive smoke emanating from his car.
Denny Hulme won, Chuck Parsons was second and Mario Andretti took third.
1969 Texas Can-Am
Both the works McLaren men could still win the Driver’s Championship heading into the season-finale at Texas but Mario Andretti sprung a surprise in qualifying and split the factory M8Bs with his Holman Moody M6B.
Siffert started back in ninth after another session had been marred with an oil leak.
Despite his cooling fan breaking late in the race, Siffert managed to finish a creditable fourth.
Bruce McLaren won after Denny Hulme retired. George Eaton finished second in his privateer McLaren M12 and Jack Brabham was third in the Alan Mann-built Ford Open Sports.
1969 Can-Am Championship Standings
Despite missing the four opening races and a somewhat disappointing end to the year, Jo Siffert ended up fourth in the final Driver standings with 52 points.
Bruce McLaren won the title with 165 and Denny Hulme was second on 160. Chuck Parsons was third on 85.
Porsche Regroups
It was obvious Porsche needed a bigger, more powerful engine to win in Group 7 but there was neither the time or money for this to be rectified straight away.
Back at the factory, a Flat 16 engine was shoehorned into chassis 027 during 1970 and experiments with turbocharging the Flat 12 began.
Subsequent History of chassis 028
Siffert’s 1969 race car was mothballed for 1970. Towards the end of that year, it was sold to Vasek Polak for the Porsche collection at his Hermosa Beach dealership in California.
Porsche and Jo Siffert returned to Can-Am in 1971 with the first generation 917-10.
Having sat unraced for 18 months, Vasek Polak’s team dusted down chassis 028 and embarked on a full Can-Am season for 1971 with Milt Minter at the wheel.
The engine was upgraded to Porsche’s latest 4907cc unit, some tweaks were made to the nose and tail and a latest type rollover bar was installed.
Now painted white and with a wide blue centre stripe, the best results for Minter in 1971 were a pair of fifth place finishes at Road Atlanta and Edmonton. Bodywork was modified during the year and eventually incorporated ugly shortened front and rear clams.
In this configuration (but with a 4.5-litre turbocharged engine) Sam Posey then did the last two 1972 Can-Am races. He scored a fifth at Laguna Seca and then retired with gearbox problems at Riverside.
For 1973, further changes were made to 028.
The ugly modified body was discarded in favour of a new soft nose 1972-type Group 7 Spyder shell. A full five-litre normally aspirated engine was fitted and the white car was given a blue noseband and centre stripe.
Vasek Polak prepared 028 for Steve Durst to drive that season.
Durst’s best result in 1973 was fifth in his opening race at Mosport. Later in the season and unhappy with the old Porsche, Durst switched to a McLaren M8F run by Motschenbacher Racing.
Before the end of the 1973 Can-Am season, Vasek Polak gave chassis 028 its final revamp.
Polak fitted a turbocharged engine and the full shovel nose bodywork that normally accompanied the forced induction engine.
Polak contracted Brian Redman to drive the plain white car in the last two races of 1973 but Redman failed to finish on either occasion.
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