Guide: Porsche 911 2.7 Carrera RS - a Historical & Technical Appraisal
BACKGROUND
Having been appointed Porsche Chairman in August 1972, Dr Ernst Fuhrmann quickly decided the company’s racing programme should focus more on the 911 as opposed to purpose-built sports prototypes.
Consequently, 1973 would mark the end for the legendary 917 which had variously dominated the Group 5 and Group 7 racing classes since 1970.
With this in mind, Fuhrmann sanctioned a last hurrah for the 917 in the shape of the extreme 917/30 which pounded the Can-Am and Interserie opposition throughout 1973. Meanwhile, a new era began for the 911.
Back in 1970, the FIA had revamped the structure of its racing regulations and created a new category for modified production-based GT cars: Group 4.
Prior to 1970, the sole Grand Touring class (Group 3) had required qualifying machinery to compete in more-or-less standard trim. Group 4 on the other hand now permitted modifications like bigger engines and wider wheels which resulted in one of the most spectacular eras GT racing had ever seen.
For the 1970, ‘71 and ‘72 seasons, Porsche built a handful of highly tuned 911 ST variants for factory use and special customers. However, development of the ST had become increasingly restricted by the production 911 on which it was based. Additionally, only around half-a-dozen examples were typically built in any given year; these were not the kind of cars that could be ordered through a visit to your local Porsche dealer.
That was to change for the 1973 season when Porsche’s Carrera RS-based RSR was made available to anyone with deep enough pockets to buy one. It would take the fight to the De Tomaso Pantera GT4, Ferrari 365 GTB/4C and Chevrolet Corvette which had thus far proved the fastest Group 4 cars available.
Whereas the De Tomaso, Ferrari and Chevrolet challengers were derived from series production models that just happened to satisfy the minimum Group 4 build requirement of 500 vehicles, Porsche took a different approach. They created a hot 911 that bristled with special features and only planned to assemble the 500 cars required by the rules – a true homologation special.
The resultant 911 2.7 Carrera RS was introduced at the Paris Motor Show in October 1972. In addition to its enlarged 2.7-litre engine, the Carrera RS came with an enhanced bodyshell, uprated suspension, wider rear wheels, custom body panels and a stripped-out interior. Saving weight was of vital importance as the competition variant (the RSR) had to tip the scales at the same figure as the homologated road car.
Manufactured on the F-series 911 platform from November 1972 until July 1973, the 2.7 Carrera RS ultimately proved far more popular than anticipated. The bean counters at Porsche initially thought the company would struggle to sell the 500 cars required for homologation, however, demand for the RS proved so strong that over 1500 were eventually completed.
During a brief nine month lifespan, the 2.7 Carrera RS was Porsche’s flagship offering. Other 911s available for the 1973 model year included the 2.4-litre 911 S (190bhp), the mid-range 911 E (165bhp) and the entry-level 911 T (130bhp).
While the 911 T, E and S were all available in Coupe and Targa body styles, the Carrera RS was manufactured exclusively as a Coupe.
It was not originally compliant for sale in the US market on emissions grounds.
CHASSIS
To save weight, the Carrera RS used a unitary steel bodyshell without the usual rustproofing and sound deadening. A lightweight floorpan was fitted and the suspension mounts were reinforced.
As usual, suspension was fully independent with torsion bars and telescopic shocks. The front end used a compact MacPherson strut arrangement with a single lower wishbone. At the rear, semi-trailing arms were installed.
Specific to the Carrera RS was a light alloy front suspension support and strengthened rear suspension arms around the wheel bearings.
Unlike the 911 2.4 S (which used Koni dampers), the Carrera RS came with lighter and stiffer gas-filled Bilstein items. Thicker anti-roll bars were installed at either end.
Ventilated disc brakes were lifted direct from the 911 S. They had a 282mm diameter at the front and 290mm diameter at the rear.
The 15-inch diameter Fuchs forged alloy wheels were 6-inches wide at the front and 7-inches wide at the rear (compared to 6-inches all round on the 911 S). Spacers of 7mm were added at the back to increase track.
Initially Pirelli and later Dunlop tyres were fitted.
An 80-litre fuel tank imported from the regular 911 was located underneath the front lid.
ENGINE & GEARBOX
Porsche developed a special Type 911/83 engine for the Carrera RS. At 2.7-litres it was easily the biggest yet fitted to a production 911.
In typical fashion, the new engine was a dry-sumped, air-cooled, all-alloy Flat 6 with single overhead camshaft valve gear.
Nickel-silicon carbide plating was used for the cylinders which enabled bore to be taken from 84mm to 90mm. Stroke remained at 70.4mm for an overall displacement of 2687cc (a 346cc gain over the 2.4-litre motor).
The 8.5:1 compression ratio and mechanical Bosh fuel-injection were carried over from the contemporary 911 S.
Peak output was 210bhp at 6300rpm and 188lb-ft at 5100rpm.
For comparison, the engine in the 2.4-litre 911 S pumped out 190bhp at 6500rpm and 216lb-ft at 5200rpm.
Porsche fitted the Carrera RS with the five-speed Type 915 gearbox that had been introduced for the 1972 model year. Uniquely, longer ratios were added on fourth and fifth along with a heavier clutch spring.
BODYWORK
Body panels were considerably lighter than any other production 911.
Thinner steel was used for the front and rear fenders, the front lid and the roof.
The engine cover was either fibreglass or steel according to which variant was ordered (M471 Sport or M472 Touring respectively).
Both types came with a distinctive Ducktail rear spoiler.
To equalise downforce, a chin spoiler was added to the new fibreglass front apron.
All four wheelarches were subtly flared.
Carrera decals colour matched to the wheel centre inlays were normally adhered down each flank. A matching Porsche script was added across the engine lid.
INTERIOR
Inside, the 2.7 Carrera RS adopted its basic architecture from the regular 911.
Behind the familiar steering wheel with its distinctive arced spokes was a five gauge dash in the centre of which was an 8000rpm rev counter. Off to the right was a 250kmh / 150mph speedometer and either a blanking plate or clock (depending on whether the car was to Sport or Touring trim). To the left were combined read outs for oil pressure / oil temperature and oil level / fuel.
The dash itself was fashioned from soft-touch black vinyl to match the door panels and rear sidewalls.
OPTIONS
Customers could upgrade their car with an array of optional extras to include a limited-slip differential, spot lights, a rear wiper, a heated rear window, tinted glass, head rests, an electric sunroof, a radio, an electric antenna, a rear nudge bar, front lid / engine cover retaining straps and a front bumper assembly with provision for a transmission oil cooler.
Decals and wheel centres could be ordered in one of four colours: black, blue, red or green. The decals could also be deleted at no cost.
In addition, buyers had to select from one of two trim levels when placing their order: Sport (option code M471) or Touring (option code M472).
CARRERA RS SPORT (M471)
M471 Sport versions came with a fibreglass engine cover, single-piece glassfibre bumpers, thinner Glaverbel glass, minimal underseal and adhesive instead of metal badges.
Interiors were equipped with fabric Recaro single-piece bucket seats, a small diameter steering wheel, thin felt carpet, rubber floor mats, reduced sound insulation, basic door trim (without armrests, grab handles or storage bins), manual window winders, fixed rear quarter windows and a simple black headliner.
Rear seats, a clock and passenger sun visor were not fitted.
CARRERA RS TOURING (M472)
The M472 Touring version came with a Comfort pack which increased the price by nearly 10% but proved extremely popular (86% of buyers chose it).
The Touring effectively came with a 911 S cabin equipped plus the normally optional Recaro two-piece sports seats trimmed with vinyl bolsters and fabric centres. The cockpit was fully upholstered; it had rear seats, a larger diameter steering wheel, conventional door trim (with grab handles, arm rests and storage bins), electric windows, a passenger sun visor, opening rear quarter windows, a better quality headliner, thicker carpet and a full complement of sound deadening.
Touring bodyshells were also properly undersealed unlike the Sport which only had its inner wheelarches coated.
Touring variants had bumpers with chrome and rubber trim inserts from the 911 S in addition to that car’s bright metal sill covers. The single-piece fibreglass rear bumper used by the Sport made way for a multi-piece steel bumper which closely resembled the regular 911 item. Fibreglass was switched to steel when it came to the engine cover. Adhesive badges became metal.
WEIGHT / PERFORMANCE
The 975kg M471 Carrera RS Sport had a 0-62mph time of 5.4 seconds.
The 1075kg M472 Carrera RS Touring had a 0-62mph time of 5.7 seconds.
Both variants had an identical 153mph top speed.
For comparison, a standard 1973 model year 911 2.4 S Coupe weighed 1050kg, had a 0-62mph time of 6.6 seconds and a top speed of 144mph.
PRODUCTION CHANGES
In order to get the 2.7 Carrera RS certified at the lightest possible weight, the first 17 production cars were built as bare bones Carrera RS H variants (H in reference to Homologation).
These early cars tipped the scales at 960kg which was 15kg less than the M471 Sport. The 15kg weight saving was thanks primarily to a lighter passenger seat, narrower wheels, no glovebox door and more basic upholstery. Most of them also came with ‘negative’ decals with coloured lettering whereas production versions used a ‘positive’ design with transparent lettering over a coloured background.
Against expectations, the 911 Carrera RS proved so popular that the entire 500-car production run quickly sold out.
Group 4 homologation was approved on March 1st 1973.
Second and third batches of 500 cars were quickly sanctioned which meant Porsche also hit the 1000-car homologation requirement for Group 3 (approved on July 2nd 1973).
Unlike Group 4 (which permitted significant modifications to the base car), Group 3 was a category for more-or-less standard machinery with just essential safety gear added.
By April 1973, Porsche was beginning to run short of some of the lightweight parts developed for the Carrera RS. As a result, later cars often came with heavier panels, steel front support bars, standard Sekurit glass and a Silumin alloy crankcase (instead of magnesium). Most examples were fully undersealed by this point as well.
WORLD SPEED RECORD ATTEMPT
On July 28th 1973, Porsche in collaboration with Martini and Continental (who wanted to promote their new TS range of tyres) embarked upon a couple of speed record attempts with the Carrera RS at the Ehra-Lessien test track in Germany.
Driving an M471 Sport-optioned example (albeit equipped with a 2.8 RSR engine), Fritz Huschke von Hanstein (Porsche’s public relations manager) set new Class A records for 10km and 10 miles runs from a standing start attaining speeds of 153.051mph and 160.484mph respectively.
END OF PRODUCTION
2.7 Carrera RS production ran from October 1972 until July 1973.
1525 were produced in total. This figure comprised:
17 to Carrera RS H trim (all of which were left-hand drive).
200 to M471 Sport specification (of which 17 were right-hand drive).
1308 to M472 Touring specification (of which 100 were right-hand drive).
For 1974, the 2.7 Carrera RS was replaced by the even more extreme 3.0 Carrera RS which was based on the heavily revised G body platform.
COMPETITION RECORD
The RSR racer homologated by the 2.7 RS for 1973 went on to have an enormously successful season. That year it won every major series contested to include the World Sportscar Championship GT Cup, the European GT Championship, IMSA and Trans-Am.
Using the 2.7 Carrera RS, Porsche also made the decision to attack the 1973 East African Safari Rally, a gruelling 5300km event through Kenya and Tanzania that was considered the ultimate test of a machine’s toughness.
Three M471 Sport-optioned examples of the Carrera RS were prepared: two official works entries and another on a preparation and service basis for a privateer effort.
Unfortunately, none made it to the finish. The works Sobieslaw Zasada / Marien Bien entry went out with gearbox trouble shortly after having been rolled while the Bill Fritschy / Kim Mandeville machine campaigned under a Chipstead of Kensington entry dropped out shortly afterwards with its own transmission woes.
The other works car, allocated to Bjorn Waldegaard / Hans Throszelius, retired just before the finish after a broken oil pipe resulted in a cooked engine.
After a preparatory outing on the 1973 1000 Lakes Rally in Finland (where Leo Kinnunen and Atso Aho finished third in Waldegaard’s uprated Safari car), Porsche made a second attempt on the Safari Rally in 1974.
The company returned with the same three cars used in 1973, but now much-improved in every key area. On this occasion, Bjorn Waldegaard and Hans Throszelius finished the 5500km event second overall while the other two cars failed to finish (both with engine trouble).
Outside of these factory efforts, privateers went on to achieve great success with the 911 Carrera RS in Group 3 trim and the car proved enormously effective in practically all disciplines of motor sport to include circuit racing, hillclimbs and rallying throughout much of the 1970s.
Text copyright: Supercar Nostalgia
Photo copyright: Porsche - https://www.porsche.com
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