Nurburgring inaugurated a 24-hour race for touring cars in 1970 primarily for amateur drivers. Taking advantage of the long 15.5-mile North Loop circuit, the event allows 200 cars to start, including, in 1971, this 911S 2.5-liter coupe. Porsche Archiv

As the 1972 season began, the racing department turned out something like 21 racing versions and two rally cars as 911 prototypes with 2.5-liter engines, the so-called 911S 2.5. According to 911 racing historian John Starkey, Zuffenhausen developed two versions of the engine. The first, with bore and stroke of 86.7x70.4 millimeters for total displacement of 2,492cc, produced 270 horsepower at 8,000 rpm. The engine, as Starkey reported, “tended to loosen its flywheel bolts or, in extreme cases, break the crankshaft. There was little doubt at the factory that this was totally due to the longer stroke being used.” The solution was a new configuration, relying on the previous crankshaft stroke of 66 millimeters inside Nikasil cylinders with an 89-millimeter bore. This created an engine with 2,466cc displacement, but through careful tuning, it matched the earlier engine’s 270 horsepower output at 8,000 rpm. Porsche had used its original Typ 901 transmission until this time, and it was durable, reliable, and distinctive with shift pattern that set first gear to the far left and rearward, reflecting the philosophy that drivers, especially racers, needed first gear only for startup and placing two-three and four-five in the same plane made for a more sensible shift pattern. But with the additional power the 2.4- and 2.5-liter engines developed, stronger gearboxes were essential. This gave Porsche the chance to satisfy the greater number of road car drivers who complained about the dogleg shift from first to second. Engineers designed the new transmission, designated Typ 915, to handle 20 percent more torque than the original transmission. They incorporated a pressure oil pump to lubricate the gears, an improvement over the original splash system. They also reconfigured the gear placement, putting first and second on the same shaft. Fifth gear moved to the far right and forward, with reverse straight behind it.

After starting 25th on the grid for the 12 Hours of Sebring in March 1972, Peter Gregg and Hurley Haywood headed to a second GT/2.5-class win in as many U.S. starts. The two won their category a month earlier at Daytona as well. Porsche Archiv

For 1972 in the States, Brundage Motors in Jacksonville, Florida, much better known by their cable address Brumos, ran Hurley Haywood in a Peter Gregg–prepared 911 ST to win the International Motor Sports Association (IMSA) Camel GT Championship inaugurated that year. While these cars had filled prototype needs, Porsche—and in particular Ernst Fuhrmann, recently returned as chief engineer—was very aware that the 911S no longer was remotely competitive in regional and national GT racing. Responding to a provocative demand from Fuhrmann, young engineer Wolfgang Berger and his bosses, Norbert Singer and Helmuth Bott, tackled the succession of challenges that were keeping Porsche 911 racers from the winner’s circle. THE 911RS AND THE 911RSR Starting with the burzel ducktail to eliminate rear lift and tame its oversteering tendencies, engineers at the new Weissach engineering center, opened in 1972, made extensive changes to the 911S. What they created became the RS 2.7 Carrera in a lightweight form (known internally as the M471) for racing homologation and a touring form (M472) to satisfy the anxious personnel in sales and marketing. (RS was the abbreviation for rennsport, or racing sport.) Porsche manufactured 1,580 of the cars, silencing the cautious sales staff and meeting not only requirements for Group 4, but also for Group 3 competition. Bott assigned Singer, an extremely clever racing engineer, to take the car further, to develop a successful racer for Group 5, a new Special Touring Car category for limited production racers that the FIA announced effective for the 1975 season.

USING GROUP 5 TO PUT ON THE BRAKES Porsche had blindsided the FIA in 1969 with its Typ 917. The racing organization had watched engine displacements grow as Ford used ever more cubic inches to push its GT40 racers to championships. The cars had topped 200 miles per hour at some circuits, and the FIA felt it was necessary to contain the speed. Starting with the 1970 season, it limited displacement to five liters, expecting that race car makers would adapt and recycle existing engines. They did not expect that Ferdinand Piëch would stretch the three-liter flateight of the 908 out to 4.5 liters with 12 cylinders. Nor did they expect Eugen Kolb’s sleek 907 and 908 bodies to grow to accommodate such power. And they never expected long-tail versions to hit 235 miles per hour along the Mulsanne Straight at Le Mans. As a result, their next round of rules called for smaller overall displacement for prototypes and an emphasis on, really, a return to silhouette racing, competing in cars derived from production models.

In Weissach’s racing department Singer and his group developed a new model known internally as the M491, the Carrera RSR (rennsport rennen, literally racing sport racer). They bored out the production M471’s RS 2.7-cylinder barrels from 90 millimeters to 92, retained the 70.4-millimeter stroke, and developed overall displacement of 2,806cc. With the 2.7 engine crankcase, crankshaft, and connecting rods; twin-plug ignition; a slightly smaller cooling fan; a front-mounted oil cooler; and 10.3:1 compression ratio, the engine developed as much as 308 horsepower at 8,000 rpm. For suspension, Singer’s group adapted the RS system, adding coil springs surrounding the stiffer front and rear struts, and fitting adjustable anti-sway bars. Brakes came from the 917, with ventilated and cross-drilled rotors, aluminum alloy calipers, and adjustable front-rear bias. They fitted 9-inch front and 11-inch rear wheels inside fenders flared out two inches per side. They relied on an 80 percent lock-up limited slip differential at the rear to get power to the ground. The cars weighed 1,980 pounds and according to racer and racing historian Jürgen Barth, Weissach assembled 57 of the cars plus two slightly heavier versions for the Corsica Rally (at 2,112 pounds with the extra reinforcement, undercarriage protection, and other gear). Porsche chose Daytona in early February 1973 to debut the RSR, offering Brumos and Roger Penske each a car to run. Since the homologation process moved slowly, the cars ran as prototypes. The race began with a full field of sports racing entries as well as GTs, some 53 cars in all. However, by the halfway point, dozens of cars had retired, leaving the event to the GT cars with Mark Donohue and George Follmer leading in Penske’s car. A collection of Ferrari Daytonas, Corvettes, Camaros, and 911S coupes followed, though Peter Gregg and Hurley Haywood in the Brumos-sponsored RSR ran within exhaust-sniffing distance of the Penske entry. At around 5 a.m., Follmer pitted with a problem highly unusual for a racing Porsche: his RSR had holed a piston. This opened the track for Brumos. At the 20-hour point, when a rock shattered their windshield, they commanded a 35-lap lead over the second-place Ferrari Daytona. The Brumos crew, under the direction of “Peter Perfect,” as Gregg was known, had rehearsed every procedure, even to changing the front glass. However, with their comfortable margin, no one hurried. At the checkered flag, Gregg and Haywood claimed the first international victory for the new car, still holding a margin of 32 laps over the Ferrari. Historian Janos Wimpffen summarized the context and importance of this accomplishment: “Gregg and Haywood were still relative unknowns at this time and their effortless win put them on the international racing map. The outcome focused attention on the potential of the Porsche 911 in its new disguise. About a decade earlier, Porsche was maturing from its reputation as merely a class winner into a competitor for overall honors. Now the same growth process was occurring to its 911 family of models. They showed they could outlast and defeat the authentic Sports category members.” Those who questioned the capability either of Norbert Singer’s new RSR or of Brumos’ accomplishment needed wait only seven weeks until Sebring when car and drivers proved themselves again. The biggest competition Gregg, Haywood, and privateer entrant Dave Helmick faced was the relentless pushing they got from the second-place RSR of Michael Keyser and Milt Minter who finished one lap down. Sebring set another milestone in 1973. By the time the green flag dropped, IMSA had achieved FIA recognition and the 12-hour race was its first sanctioned as part of the World Championship for Makes (WCM). The FIA had homologated the RSR in Grand Touring class by the time the series returned to Europe for the season there. The car, with a wide variety of owners and drivers, was indomitable in its class, and often another of the Porsche factory RSRs followed it to a second-place finish. An early-season protest gave Norbert Singer the opportunity to run the factory entry as a prototype and it became his rule-bending test platform, on which he experimented from one race to another with body and suspension modifications. One often-seen rear wing configuration took extensions from the ducktail and ran them off to the side, blending them into the wide flares. Klaus Reichert, who was press boss and Porsche’s staff photographer at the time, nicknamed it the Mary Stuart collar after the British queen known for her high neckwear. Singer also tested a long tail, which stretched the rear deck lid several feet past the end of the body and capped it with two vertical wings.

At the last-ever Targa, run on May 13, 1973, Porsche’s thoroughly developed Carrera RSR2.8 proved strongest of the day taking 1st overall with Gijs van Lennep and Herbert Müller sharing driving duties. The car wore a prototype “Mary Stuart collar” rear wing that widened the aerodynamic aid to full-body width. Porsche Archiv

Singer and his Weissach colleagues developed a three-liter version of the RSR engine by enlarging cylinder bore from 92 millimeters to 95. The new engine’s 300 horsepower, 30 more than the previous displacement, led to failures in the magnesium crankcases so engineers reverted to aluminum. The FIA approved the new engine in early May, in time for Le Mans trials and the race. For 1974 and 1975, the car’s designation changed to Carrera RSR 3.0 (with a corresponding RS 3.0 homologation model for road use and racing in Group 3). During this time the factory car ran in Martini silver, blue, and red livery. Thinner-gauge steel, some plastic components, and fiberglass front and rear bumpers, deck lids, and a larger rear spoiler—as well as a single Recaro high-back racing seat, rollover bar, onboard fire extinguishing system, 29-gallon fuel tank, and dual fuel pumps—characterized the 2,024- pound RSR. Weissach assembled 109 of the 3.0 models: 56 as road-going RS versions, 42 as the race-prepared RSRs, and a special run of 15 more for Roger Penske for a series that Ontario Motor Speedway developer David Lockton created, called the International Race of Champions (IROC). For the inaugural season, IROC cars used RSR engines in RS bodies with the smaller burzel. IROC was an entertaining series of four events that invited a dozen legendary drivers from NASCAR to race against Indy car racers and endurance racing veterans in identically prepared cars. Penske painted the Porsches in vibrant colors with the driver’s name in bold letters on the sides and windshield. Mark Donohue won three of the four races to take the title. Because few of these racers were familiar with Porsche’s handling, Porsche’s was a one-year involvement and for the next 15 years the IROC series ran in Camaros. For 1975, Weissach assembled only another 12 RSR coupes with no changes from 1974 specifications. Porsche built these for customers to replace cars damaged or destroyed in crashes.

Working from his close relationship with Porsche racing and its 917/30 Can-Am cars, team owner Roger Penske helped devise a match race series using new Carrera RSRs. Mark Donohue won the four-event contest, called the International Race of Champions, starting with victory here at Daytona. Porsche Archiv

At the Nurburgring 1,000-kilometer race two weeks after the Targa, van Lennep and Müller served notice on the Sports Racing community. In their RSR 2.8, fitted with a 3.0-liter prototype engine they finished fifth overall behind a pair of Ferraris, a Chevron and a Porsche 908. Porsche Archiv

WORLD POLITICS AND RACING In October 1973, the 11-member Organization of Arab Petroleum Exporting Countries (OAPEC) raised crude oil prices 17 percent. A day later, it began reduced oil deliveries by 25 percent and promised 5 percent less oil each to nations supporting the state of Israel. Few citizens and fewer racers envisioned the long-term effects this caused. Although OAPEC lifted the embargo in March 1974, gasoline prices at the pump had risen dramatically. Lines at gas stations stretched for a block and then further. State governments in the United States implemented rationing. As the impact hit Europe, Germany and other countries adopted no-drive Sundays and strict limits on purchases. In view of this, racing seemed frivolous if not irresponsible. IMSA and the FIA canceled the 24-hour race at Daytona and the 12-hour Sebring event for 1974. They shortened 1,000-kilometer endurance races to 750. Politicians and engineers began considering that if racing were to survive, it had to benefit road-going cars, not just provide entertainment. Le Mans, which always had maintained a category called Index of Performance for the most fuel-and-materials efficient racers, introduced a new formula emphasizing consumption for 1975. This required cars to complete 20 laps between fuel stops. The FIA Group C, first contested in 1982, was the direct outcome.

The 1974 version of the RSR used a 2.14-liter turbocharged engine to develop 500 horsepower. Installed in a race car weighing 1,764 pounds, performance was impressive. Porsche Archiv

With neither Daytona nor Sebring contested in 1974, the World Manufacturers Championship first met at Monza in late April. John Fitzpatrick and owner Georg Loos won the three-liter Grand Touring class in Loos’ RSR, a feat they repeated two weeks later at Spa in Belgium with Jürgen Barth substituting for Loos. The shortened 750 kilometers of Nurburgring made it three in a row for Loos/Fitzpatrick/Barth. A Kremer Brothers RSR took the class win at Imola in Italy while other privateers claimed second overall and first in class at the Targa in early June. At Le Mans, the Automobile Club de l’Ouest (ACO) organizers classified Singer’s prototype turbo RSR in the same three-liter Sports category as home-favorite Matra. Horsepower and aerodynamic differences between the low, open-top prototype and the 911 with its big wing made it inevitable that factory-backed Herbert Müller and Gijs van Lennep followed the Matra and they finished second overall and second in class. Normally aspirated RSRs finished a season in which the Kremers took class wins at Austria, Gregg/Haywood won at Watkins Glen, and successive victories occurred for Georg Loos at Paul Ricard, Brands Hatch, and far-off Kyalami in Union of South Africa. In the United States, Gregg’s win at the Glen helped him and Brumos seal the 1974 IMSA championship as well. When he wasn’t running IMSA weekends, he competed in the SCCA Trans-Am. Organizers there were smarting from the loss of American manufacturers, who, with coming emissions and safety regulations, believed they had accomplished all they could in racing. To fill out thinning starting grids, the Trans- Am welcomed Porsche back. However, IMSA had captured spectator, manufacturer, and sponsor interest. Their races were well attended and well supported, unlike the SCCA events. Peter Gregg won the championship in 1973 and repeated in 1974, a season shortened to just three events from lack of support.

RIPPED FROM THE PAGES OF A FRENCH NOVEL For Le Mans in 1974, Matra ran with a new gearbox that Weissach developed for them as outside clients. At about 11 a.m., with five hours to go, Matra driver Henri Pescarolo had an 11-lap lead over the RSR prototype. Pescarolo lost fifth gear and then seemingly all his gears. He found third and limped to the pits. As historian Janos Wimpffen reported in Time and Two Seats, “For over half an hour, the Matra crew toiled before they discovered . . . the sleeve between two gears had dislocated.” They quickly reassembled the gearbox, but during the 45 minutes it required, the second-place RSR had been unlapping itself. Except that it, too, was using the transmission and had lost fifth gear. Singer, as race director, told his drivers to take it easy and run about 45 seconds off the pace. Of course, as part of Matra’s purchase agreement with Porsche, “the factory technicians had to walk over to the Matra pits and contribute to their own ultimate defeat.” When Pescarolo’s Matra reentered the track, he and Müller’s RSR were on the same lap. The Matra was nearly good as new, while the Porsche still suffered. By the end, Pescarolo had put six laps back on Müller. “Pescarolo even had time,” Wimpffen continued, “to make a leisurely stop for fresh tires and a little freshening of both car and driver, making them properly photogenic at the drop of the flag.”

Porsche was first on the track with FIA rules–compliant Group 5 cars. Derived from the production 930, this first-generation 935 weighed 2,138 pounds and its 2,856cc turbocharged engine developed 590 horsepower. Porsche Archiv