The 1973 Porsche RSR Story

The background to Car R7 & the ‘Mary Stuart’ Tail

In 1973 Porsche produced 48 2.8L RSR racecars primarily to achieve its aim of dominating Group 4 [GT Cars]. These mostly privately entered cars dominated the GT class & won 7 out of 9 races in the World Sports Car Championship in 1973.

Porsche took 2.7L RS’s from the assembly line & sent them to the competition dept for conversion to M491 specification. The factory also made 8 ‘Factory Cars’, known as R1 thru to R8, which started life as M491 spec 2.8L RSR’s. In 1973 Porsche ran two factory prepared Carrera’s at each World Sports Car event, sponsored by Martini Racing, one mainly in Group 4 [GT Class], whilst one was run in Group 5 [Prototype Class] & developed during the season. Notably the privately entered Brumos Group 4 GT configured Carrera, recorded Porsche’s first outright Makes victory with an RSR, at the season opener, the Daytona 24hr in March.

Factory cars R6 & R7 were the 2 cars mainly used in the prototype class & developed as such during 1973.

The full width ‘Mary Stuart’ rear spoiler enveloping the rear part of the body was first seen mocked up with standard RSR flares on R8 at the Monza 1000km race in April. It was lighter too, with fiberglass panels for the doors, both bonnet lids & Perspex replacing all the glass except the front windscreen.

After successful track & wind tunnel tests a similar setup on R6 was taken to the Targa Florio in May 73. Driven by Lennep & Muller, one of 4 Factory Martini entries, R6 was a surprise winner in the famous Sicilian road race.

By the ‘Le Mans 24hr’ in June development on R6 [race #47]& R7 [race #46] had the final version of the ‘Mary Stuart’ tail & Group 5 Prototype Class changes included the following:

• The ‘Mary Stuart’ tail, which encompassed 2-inch wider rear guards & flares with the large enveloping rear body spoiler flowing into the Std RSR Duck Tail.
• 2-inch wider front flares.
• The wheel rim sizes were increased in width to 10.5” on the front & 14” on the rear & were suitably shod with wider slicks than the Group 4 GT cars.
• The rear suspension pivot position changed [15mm towards the center &
• 47.5mm rearwards] & the rear suspension arms were shortened.
• An increase in the bore from 92mm to 95mm, so increasing the capacity from 2.8 to 3.0L, using alloy cases.
• Fiberglass doors, in addition to front & rear bonnet lids & bumpers.
• Perspex for all glass except the front screen.
• A drastic reduction of interior trim. Thus some 50kg was saved over the Std Group 4 car.

In late June 73 at Zeltwag R6 was sporting an even larger rear wing that would go on to develop into the body style used on the 74 Martini Turbo 2.1 Factory Group 5 cars. R7 also ran at this event in its ‘Le Mans’ setup.

The next event was the Watkins Glen 6hr in July 73, both R6 & R7 ran the larger 74 Turbo style wing, but with 3.0L engines, finishing 6th & 7th O/A.

The Factory Martini Cars developed continually during the 73 season running in the Group 5 Prototype class and were instrumental in the design of the 74 Factory Martini 2.1 Turbo & the 74 3.0L RSR customer racecar.

The car we have replicated is R7 [using a 73 911 T shell, chassis #911 3501046] in the mode in which it ran at the Nurburgring, Le Mans & Zeltwag events during the months of May & June 1973. In fact in this guise R7 only ran in 3 events, both R6 & R7 never survived intact in this configuration. At season end they had mockup style 74 rear ends with 3.0L engines. They were returned to Std M491 RSR spec by the Porsche Race Dept & sold to private race teams.

R6 & R7 survive today in private ownership & have been restored back to 73 ‘Le Mans’ Spec, having had there “Rear Ends’ reproduced from period photo’s.

References

- Porsche 911 Story, by Paul Frere.

- The Racing Porsche R to RSR, by John Starkey.

- RacingSportsCars.com