911 and Porsche World
In 1976 FIA changed the international rules for Group 4 cars requiring that instead of production of 500 cars being required in one year that only 400 were required to be built over a period of two years. The rules change also reduced the modifications that were allowed and applied a weight scale that was relative to the engine size instead of homologated weight as it had been before. This new weight rule had two purposes: one was to reduce the manufactures cheating on the homologation weight and the other was to allow more luxurious cars that would naturally be heavier to be competitive in the restructured class. With this new rule change there was no longer a need for special lightweight models of a production model such as the Carrera RS 2.7 and RS 3.0 because the weight would be based on the engines size and not the homologation weight. So as a result of these new rules any car could be lightened to the limit determined by the engine size. There was also a scale limiting the tire width proportional to the engine capacity for the Group 4 category as well.
Porsche introduced the 930 Turbo Carrera in 1975 as their basis for a Group 4 race car. Their intent was to build 400 of the 930 Turbo Carrera over the required two year period. The rule changes finally came in 1976 and Porsche produced two new 911 race cars for the new classes that were based on the production 930 Turbo Carrera, the 934 and 935. The 934 was homologated as a Group 4 car and sold to racing customers for GT racing. The 935 was a Group 5 car and as such was required to be based on a production car that homologated in groups 1 to 4. For 1976 the Porsche factory built and raced two 935s and raced the cars exclusively themselves and won the 1976 World Championship of Makes in the Group 5 category.
The basis for the homologation of both the 934 and the 935 was the series production 930 Turbo Carrera and the requirement was for 400 to be produced in two model years. Because the 934 was supercharged with a turbocharger the displacement of the engine had its actual displacement multiplied by 1.4 and considered to be a 4.2 liter engine. Because of the 1.4 multiplier for turbocharged cars the 934 Turbo RSR could not be considered a light weight model like its predecessor the 3.0 RSR had been. The multiplier placed the 934 in the 4001 to 4.500 cc class requiring the cars weight to be 1,120 kg (2469 lbs). The 934s had power Windows and still required 88 lbs of lead in the front trunk to bring them up to weight. A new Porsche 934 sold for DM97,000 ($28.000 US) in 1976 delivered ready to race.
Because of the Group 4 rules the 934 was very closely related to the production 930 Turbo Carrera. The most obvious visual changes were the added on fiberglass fender flares and the front fiberglass air dam with openings for the oil cooler, brake ducting and the water radiators for the engines intercooling. The rules allowed extending the front fenders by 50 mm and the rear fenders by 100 mm which was approximately 2 and 4 inches respectively so these fender flares extended all around the standard openings by 50 mm in the front and 100 mm in the rear. The 934s had an aluminum roll cage and some aluminum cross bracing to structurally increase the torsional strength of the body. A large 120 liter (31.7 gallon) safety fuel cell and a front mounted 22 liter (5.8 gallon) dry sump oil tank filled up most of the front trunk area.
The interior was simplified, but retained most of the interior features of the production series 930 Turbo Carrera including a standard headliner, the power windows and Leatherette upholstery on the door panels. The rear seat was left out and the dash was simplified, and a Porsche racing seat and six point seat belts were added in place of the standard driver and passenger seats. The standard gauges were used for tachometer, oil pressure and temperature and additional gauges were added for fuel pressure and fuel injection system pressure. The windows remained glass because the rules required that the original material be retained.
The suspension was based on the standard 930 Turbo Carrera torsion bar suspension, but suplemented with Bilstein shock absorbers fitted with coil over springs. The suspension was stiffened by the addition of Delrin bushing on the front A arms in place of the rubber used on the series production car and in the rear they used a spherical joint on the inner end of the cast aluminum trailing arm and a ball bearing race around the outer end of the rear spring plate. The larger disc brakes from the 917 and Carrera RSR 3.0 were used with large radially vented and cross drilled brake rotors and the heavily finned aluminum calipers. The brake bias was controlled by a dual master cylinder pedal assembly with a bias bar adjustment. They also used the same center lock hubs that had been used on the Carrera RSR 3.0 They went to a sixteen inch wheel and tire combination to provide a larger foot print and adequate room for the large brakes. Because no Porsche cast magnesium wheels were available in the sixteen inch size they had BBS make modular wheels with a cast center for the 934s.
The engine and transmission were also based on the production 930 Turbo Carrera, units. The crankcase, crankshaft, rods and were essentially the standard 3.0 liter Turbo parts. The engine had a flat fan in place of the standard vertical fan for improved cooling. The flat fan was driven by a horizontal shaft up through a set of bevel drive gears to drive the fan. An adaptation of the Bosch K-Jetronic fuel injection was used on the initial 934. While the original 930 Turbo Carrera did not use an intercooler the 934 used a pair of water to air heat exchangers one above each intake manifold which reduced the charge air temperature from 150°C (302°F) to just 50°C (122°F). The water was circulated by a water pump mounted on the right bank of cylinders, and driven from the end of the camshaft, to a pair of front mounted water radiators. Porsche used a KKK turbocharger and wastgate that similar to what they had used on the 917 Can-Am cars and the Turbo RSR. They used a couple of different racing camshafts for turbocharged racing engines as they developed the engine and initially with 1.3 bar boost the engine produced around 485 horsepower, later versions of the engine with mechanical fuel injection produced as much as 600 horsepower.
The transmission was essentially the standard 930 four-speed transmission that had been developed for the production Turbo. They added and gear driven oil pump and mounted an oil cooler for the transmission up in the rear wing where the A/C condenser mounted in the production 930. The rules only allowed three different ratios for each gear set so Porsche offered three different rations for each of the four gear sets plus three different final drive ring and pinion sets. The differential was a ZF limited slip with a 80% locking factor.
Thirty one of these group 4 934s were produced for Porsche's racing customers. Most of these cars remained in Europe and competed in the Group 4 category, where the 934 was an immediate success and Toine Hezemans won the European GT Championship for 1976.
Several of the 934s were used in Group 5 category and Porsche supplied a kit that consisted of wider fender flare extensions to cover the wider tires permitted by the group 5 rules as well as a larger rear wing like those used on the later customer version of the 935s. These cars were considered by the entrants to be Group 4 1/2 cars running in support of the factory entered. 935s.
The car in our story, chassis number 93060700155, which now belongs to California Porsche collector Dave Morse, was originally purchased by Egon Evertz and driven by himself and Leo Kinnunen in the 1976 world championship events as wells Group 5 races in Germany.
Evertz and Kinnunen had a successful debut in the orange 934 at Mugello, Italy, March 21, 1976, winning the group 4 category and placing third overall behind the factory 935 and Kremers Group 5 Turbo Porsche. This was the first 934 to win in Group 4 competition in the first race of this new formula. They were not so lucky at the second race at Valleunga, also in Italy , where about half way through the race the dropped out with and engine problem. The third race of 1976 was Silverstone where the car was entered with its Group 5 conversion kit. Evertz and Kinnunen actually lead overall several times before falling back with a misfiring engine. In the fourth race of the season at Nurbürgring they went out after two hours with transmission problems.
At round five at the Osterreichring Kinnunen qualified the car second to the factory 935 driven by Jacky Ickx and Manfred Schurti. The factory 935 was delayed when the throttle cable broke and Porsche put their driver, Manfred Schurti, in the Group 4 1/2 934 in place of car owner Egon Evertz in an effort to make up time after and early pit stop by Kinnunen when he had a puncture. This was not a legal substitution since Schurti had not qualified in the car and the car was disqualified and retired. After Osterreichring Porsche was ahead in the World Championship of Makes, but just barely, leading BMW by 82 to 78 points. So, for the sixth round in the championship at Watkins Glen in addition to the normal entry of Ickx and Mass Porsche added a second 935 driven by Stommelen and Schurti and supported the entry of Kinnuen/Evertz/Hexemans in Evertz’s converted 934. The factories effort paid off with their Stomelen and Schurti 935 winning, and Evertz’s converted 934 placing second driven by a Finn, a Dutchman and a German just ahead of Mass and Ickx in the other factory 935.
Porsche left the US leading the World Championship of Makes over BMW 102 to 88 with only one championship race remaining at Dijon, France. Evertz and Kinnunen placed fourth at Dijon behind three other Porsche 935s.
The 934 as sold to Kannacher at Krefeld, but returned to Evertz and raced very little during the 1977 season. The next owner was Kenneth Leim who bought the car without the Group 5 conversion parts to contest the Group 4 category. Leim rebuilt the car to Group 4 specifications in Sweden and painted it white. Leim ran the car with Kurt Simonsen at Nurburgring in 1977 where they finished 9th.
Kenneth Leim still owned the 934 in 1978 and he and Simonsen ran the car again at the third race of the season the Dijon, France 6 hour race where they placed 9th overall and second in the Group 4 class. For the fourth race of the 1978 season at Silverstone Leim partnered with Italian lady driver, Lella Lombardi placed 15th overall. Kenneth Leim and Kurt Simonsen appeared in other rounds in 1978 with disappointing results. 1979 was not much better for the Leims team, but with an 8th at Silverstone and 16th at Brands Hatch showing that the car was still competitive.
In late 1979 the 934 was purchased by Richard Cleare. The Autofarm crew stripped the car to a bare chassis and did a comprehensive rebuild of the chassis, suspension, transmission and engine. By the time they got the car it was showing signs of the wear and tear and four seasons of racing. They had the car ready by the March 1980 race at Brands Hatch looking resplendent in its new red paint. Driven by owner Richard Cleare and Tony Dron the car was leading the Group 4 class when it had to be withdrawn with a suspension failure with Dron at the wheel. The team was more successful at their second race, Silverstone in May 1980 where Cleare and Dron placed 8th overall and won the Group 4 class. Their next race was Vallelunga where Cleare and Dron again won the Group 4 class and placed 10th overall. Their final race for the 1980 season was Dijon where they again won the Group for class and placed 11th overall. In its fifth year of international competition the 934 had shown itself to be competitive and reliable winning the Group 4 class in 3 of the 4 races that they entered.
Richard Cleare ran the 934 again in 1981 partnered at Silverstone by Andy Rouse. At the first race of the season at Silverstone Cleare and Rouse were running second to one of the then new 924 GTR Turbos when an oil line came lose and a resulting engine fire put them out at five hours. Partnered by David Kennedy Cleare‘s next race with the 934 was Nurburgring. An accident early in the race resulted in an off course excursion and the hot engine refused to restart and the team lost 30 minutes before it refired and Kennedy was able to get back to the pits where Cleare took over the driving chores. The car was finally placed 49th after the raced was stopped because of a fiery accident that cost the life of Porsche 908/3 pilot Herbert Muller. The next race in 1981 was Brands Hatch where Richard Cleare and David Kennedy were second in class after a stuck fuel catch bottle dropped them to second place a lap behind the Group 4 class winning Canon 924 GTR.
In preparation for the 1982 Season Cleare returned the 934 engine to the factory where the cylinder heads were modified and mechanical fuel injection was fitted in place of the original CIS system. The result was a power increase from 500 hp to 600 hp. Tony Dron returned to the team for the 1982 season and in their first race at Monza they placed 9th overall and won the Group 4 class. While they were at Monza the team learned that after three years of trying that they had finally been accepted for the 1982 Le Mans 24-hour classic. This was the seventh season of racing for the 934 and the car would finally see its first 24 hour race. After some difficulties with the transmission Cleare and Dron placed second in the Group 4 category and 19th overall at the May Silverstone race. They also had some handling problems which were traced to changes that they had made in the cars ride height to extend the life of the rear axles. The CV joints were showing excessive wear because of the engines extra power and the axles were having to be replaced after each race.
For the 1982 Le Mans, probably the most significant race of the 934‘s illustrious career, Tony Dron turned a time of 4.04.08, which was the fastest time ever turned at Le Mans by a Porsche 934. The team had a few problems during the race and had to replace both rear axles, but even so the 934 driven by Richard Cleare, Tony Dron and Richard Jones completed 2466.97 miles for and average of 102.79 mph winning the Group 4 class and placing 13th overall in the 1982 Le Mans race.
At Spa in September 1982 Cleare and Dron places second in the group four class and 16th overall. The next race was at Mugello and Porsche persuaded Richard Clear to take his 934 because of its reliability. Porsche promised to supply new axles, but none were available and after five hours the 934 dropped out when the right axle failed. The 1982 Brands Hatch race was the final outing for the 934 in a World Championship race where the car again won the Group 4 class and placed 14th overall. Thus ending the racing career of seven seasons of the most successful 934 to race in international competition.
Dave Morse bought this 934 in the summer of 1985 and has run it in an number of club events beginning and extensive restoration a few years ago. The car was restored to its original condition in the original orange color and completed in time for the 1998 Monterey Historics where his son Mark Morse drove it in the fifty year event at Monterey.