Guide: Last Minute Maestro - a Historical & Technical Appraisal of the Porsche 936 / 76
BACKGROUND
For 1972, the FIA’s dropped its Group 5 category for up to five-litre Sports cars which had met a 25 unit production requirement. Over night, the Porsche 917 and Ferrari 512 became pretty much obsolete. From ‘72, the World Sportscar Championship would only cater for Group 6 Prototypes (with no minimum production requirement and engines of less than three-litres) and Group 4 Grand Touring cars (of which at least 500 had to have been completed).
With nowhere left to run its normally aspirated 917 Coupes, Porsche switched to Can-Am racing where it ran turbocharged 917 Spyders with great success.
1972 was also significant as the FIA announced that, from 1975, the World Sportscar Championship would move away from Prototypes in favour of a new production-based formula where cars had to maintain the fundamental profile of a production car but little else. With manufacturer participation in the Prototype category having dwindled in the years prior, it was hoped a World Championship contested by these Group 5 Silhouette cars that bore a closer resemblance to vehicles available off showroom floors would encourage more firms to get involved.
When, towards the end of 1974, the FIA announced with little notice that the introduction of Group 5 regulations would be pushed back until 1976 because firms like Alfa Romeo, Alpine-Renault and Ligier wanted to carry on racing their Group 6 Prototypes, Porsche (who had been preparing for the Group 5 era with a 2.1-litre turbocharged 911 RSR throughout the ‘74 season) decided to sit out the 1975 campaign in protest because it did not have a suitable car to challenge for overall wins.
That was the official line anyway, but in reality, Porsche quietly supplied the privateer teams run by Reinhold Joest and Herbert Muller with updated 908/03s powered by further evolutions of the turbocharged 2.1-litre engines.
With the Group 6 versus Group 5 situation still not having been amicably resolved, the FIA later dropped another bombshell when it elected to simultaneously run separate World Championships for both categories in 1976. This would enable manufacturers with Group 6 Protoypes to continue to campaign their cars (in what was dubbed the World Championship for Sports Cars) without eclipsing the new generation of Group 5 machinery (which would contest the World Championship of Makes).
The Le Mans 24 Hours, which was not part of either series in 1976, would allow both sets of vehicles to go head-to-head.
Despite having already invested heavily in its Group 5 programme, Porsche did not want to sit another season of top flight Prototype racing out and, in September 1975, the Stuttgart firm gave the green light for what would be a hastily prepared Group 6 Prototype that could go racing in 1976.
Sufficient backing to field a single car entry in the World Championship for Sports Cars and a two-car entry at the Le Mans 24 Hours was secured from Martini & Rossi (who were also title sponsors of the Group 5 campaign).
The resultant Porsche 936 was created in very short timeframe and in great secrecy over the winter of 1975-1976. Aside from a new chassis, body and fuel cells, most of the parts were imported from existing models like the aforementioned 908/03 and also the 917 K for which Porsche still had a good stock of components sitting around.
Following a shakedown at Porsche’s Weissach proving ground, the 936 headed to Paul Ricard for a series of proper tests alongside the 935 during the last week in February 1976. The handsome new Spyder was officially unveiled at a Weissach press conference during the second week of March and made its competition debut in the opening round of the 1976 World Championship for Sports Cars: the Nurburgring 300km on April 4th.
CHASSIS
Without sufficient time to develop a monocoque chassis, Porsche opted to go with a partially skinned aluminium spaceframe with the engine serving as a stress-bearing member. To optimise weight distribution, the fuel tanks (which had a combined 160-litre capacity which was the maximum permitted by Group 6 regulations) were housed between the engine and cockpit bulkhead.
The wheelbase measured 2400mm.
Items like the springs, shocks, anti-roll bars, uprights, wheel hubs, brake system and steering were off-the-shelf components left over from the 917 programme.
The suspension layout comprised double wishbones all round with variable rate coil springs, adjustable Bilstein dampers and an adjustable anti-roll bar at both ends.
Brakes were cross-drilled and ventilated discs with aluminium alloy calipers running off a twin circuit hydraulic system with cockpit adjustable bias.
Initially the 936 broke cover with 15-inch diameter centre-lock cross spoke BBS wheels that were 10.5-inches wide at the front and 15-inches wide at the rear. The 265/565 and 340/600 tyres were supplied by Goodyear.
ENGINE / TRANSMISSION
In the engine bay was the latest iteration of Porsche’s 2.1-litre single turbo air-cooled Flat 6 as seen in the works 911 Carrera RSR Turbo of 1974 and then supplied to the likes of Reinhold Joest and Herbert Muller for their 908/03s in 1975.
The Type 935/73 motor featured a block and heads fashioned from aluminium alloy and a crankshaft in magnesium alloy. A two valve per cylinder set up was retained along with single overhead camshafts per bank, dry-sump lubrication, mechanical Bosch fuel-injection and an intercooled KKK turbocharger with maximum boost pressure of 1.4 bar.
Displacement was 2142cc thanks to a bore and stroke of 87mm and 60mm respectively. This gave the 936 a swept volume of 2998.8cc when the FIA’s 1.4 multiplier for turbocharged engines was taken into account and meant the 935/73 motor came in just below the three-litre limit for Group 6 Prototypes.
With a compression ratio of 6.5:1, peak output was 520bhp at 8000rpm and 356lb-ft at 6000rpm.
The compression ratio was soon increased to 7.0:1 which yielded an additional 20bhp.
Transmission was through a five-speed gearbox and driveshafts imported from the Group 7 917 along with a triple-plate Borg & Beck clutch and limited-slip differential.
BODYWORK
Group 6 regulations permitted either fully closed Coupe or open Spyder bodywork. Porsche opted for the latter and effectively created a more slippery, fully lit version of the Group 7 917/10 and 917/30 which had raced so successfully in the Can-Am and Interserie championships a few years prior.
The fibreglass body was formed in three main sections.
The front clip was characterised by its large rectangular nose intake for the brakes and radiator, outboard of which were twin headlights per side mounted underneath contoured Plexiglas covers. Heavily vented fenders allowed air to escape from the wheel wells. Another vent (this time for the radiator) was carved out from the sunken central plane ahead of the wraparound cockpit shroud.
Access to the cockpit was via a pair of flimsy butterfly doors. Behind the seat was a hefty exposed rollover hoop.
The rear bodywork incorporated a distinctive bulge behind the exposed horizontally mounted engine cooling fan along with myriad NACA ducts. There was also a massive adjustable spoiler with fully integrated swept back endplates and a central vane to aid stability.
INTERIOR
By modern standards the cockpit was a pretty scary place to be as there was obviously little in the way of crash protection and the driver’s feet were positioned well ahead of the front axle.
Aside from a proper driver’s seat (trimmed in fireproof fabric) and a token passenger bucket, there was no upholstery to speak of as Porsche left the aluminium spaceframe and fibreglass floor exposed.
Directly ahead of the three-spoke leather-rimmed steering wheel was a large rev counter, off to the left of which on the basic aluminium dash panel were smaller dials for oil pressure, oil temperature, turbo boost and fuel along with a variety of warning lights and flick switches.
A right-hand drive steering layout was adopted along with right-hand side gearchange.
WEIGHT / PERFORMANCE
Porsche quoted the 936 at 720kg.
Top speed as achieved down the Mulsanne Straight at the Le Mans 24 Hours was 217mph.
0-62mph likely took around 2.5 seconds depending on gearing.
PRODUCTION
Two copies of the 936 / 76 were built.
Chassis 001, the prototype tested at Weissach and Paul Ricard, made its debut at the opening World Championship for Sports Cars race: the Nurburgring 300km on April 4th. It did two more races in 1976 (now in white Martini livery), the Le Mans 24 Hours and Dijon 500km.
Chassis 002 (depicted above), which featured an array of updates, made its debut at round two, the Monza 4 Hours on April 25th, and did five more races that season (the Imola 500km, Le Mans 24 Hours, Enna-Pergusa 4 Hours, Mosport 200 miles and Salzburgring 300km). This car always ran in a white Martini livery).
PRODUCTION CHANGES
Porsche made several updates to the 936 during the 1976 season.
By the time the original car (chassis 001) made its debut at the Nurburgring 300km World Championship race in early April, the original cross-spoke wheels had been switched to five-spoke items and 16-inch wide rear wheels were fitted after the first day of practice.
At the Monza 4 Hours three weeks later, the 936 ran with a taller rear spoiler and modified throttle linkages.
The second 936 (chassis 002) that debuted at Le Mans in the middle of June featured a raft of changes exclusive to this latest iteration. The most obvious update was a dramatic new rear clip with fully enclosed engine and roll hoop topped by enormous intake snorkel. The tail fascia was also lightly re-modelled. At the front of the car, modifications included a slightly bigger chin spoiler, a NACA duct to cool the cockpit and a slim Plexiglas windsdhield.
COMPETITION HISTORY
Porsche’s main challenger during the 1976 World Championship for Sports Cars was the Alpine-Renault squad which ran a pair of its super quick A442 Turbos throughout the year. There were also a trio of appearances from the works Alfa Romeo team with a single new monocoque chassis 33/SC/12 while the likes of Mirage and March also attended certain races with their three-litre Group 6 Prototypes.
Porsche elected to run just one 936 at each World Championship race.
Round one, the Nurburgring 300km, saw Rolf Stommelen split the Alpine-Renaults in qualifying and after the French cars crashed out early on it seemed the black 936 was set for any easy win. However, a sticking throttle dropped the Porsche down the order and Stommelen had to use the ignition to cut the throttle which later caused him to spin. The 936 ultimately finished a disappointing fifth.
At the Monza 4 Hours Porsche put on a textbook demonstration of how to go endurance racing and, in the hands of Jochen Mass and Jacky Ickx, the now white 936 took pole and won by two laps from the second place Alpine-Renault.
It was a broadly similar story at the Imola 500km four weeks later where Alfa Romeo made their debut appearance of 1976. Having qualified third, Mass and Ickx took the win while Porsche’s rivals all suffered from bad decision making or reliability issues.
Porsche then ran both 936s at the non-championship Le Mans 24 Hours with the new car allocated to Jacky Ickx and Gijs van Lennep while the older version went to Reinhold Joest and Jurgen Barth. The Porsches started second and fifth respectively and looked set for a dominant one-two finish until the 16th hour when Joest and Barth retired with transmission failure. Ickx and van Lennep went on to win by eleven laps and the 936 became the first turbocharged car to take victory at Le Mans.
The World Championship resumed two weeks later with the Enna-Pergusa 4 Hours where Mass and Stommelen qualified fourth behind the Alpine-Renaults and Alfa Romeo.However, all these faster cars from practice retired and the Le Mans-winning 936 was ten laps clear of its closest rival when rain brought proceedings to a premature halt.
The result at Enna-Pergisa meant Porsche secured the 1976 World Championship for Sports Cars with three races still to run.
At the Mosport 200 mile race in late August Group 7 cars were permitted to race. Ickx qualified the Le Mans and Enna-Pergusa-winning car fastest of the Group 6 entries in third and that’s where he finished after the Alpine-Renault challenge failed to materialise once again.
At the Dijon 500km in early September Porsche reverted back to the original 936 for its first race since Le Mans. Mass and Ickx split the Alpine-Renaults in qualifying. After the Porsche got to the first corner in the lead, shambolic race management from the French squad meant Porsche took yet another win.
After a dismal year, Alpine-Renault failed to turn up for the season-ending Salzburgring 300km where the solitary Alfa Romeo took pole and set fastest lap before retiring with 16 laps after an engine failure. Against limited opposition, Mass took the 936’s fifth outright and sixth Group 6 win of the year driving 002.
For 1977, Porsche elected to focus exclusively on the Le Mans 24 Hours where it ran an updated twin turbo 936. Renault switched focus to Formula 1 which left Alfa Romeo, who now had a turbocharged 33/SC/12, to walk that year’s World Championship.
Text copyright: Supercar Nostalgia
Photo copyright: Porsche - https://www.porsche.com
