Model history: To continue the manufacturer's stronghold in the sub-2 litre GT racing class, Porsche set out to design a completely new car in 1963. This decision was sparked by the introduction of new cars from Abarth and Alfa Romeo, designed specifically for the GT class. Porsche's line up for 1962 consisted of the 356 Carrera 2, which was equipped with a two litre version of Porsche's quad cam four cylinder boxer engine. It was basically a modified road car and the German manufacturer figured more was required to take on the new Italian competition.
For homologation purposes, at least 100 examples of the new car had to be produced in twelve months. This would require a road going version, because Porsche was highly unlikely to sell 100 full blown racers. In order to free resources for the project, the expensive Formula 1 program was dropped. In theory the development costs of the GT racer would be earned back by selling them. The F1 project on the other hand did not offer much in return, except for the potential strengthening of the manufacturer's racing heritage.
Porsche's engineers had to start with a clean sheet, because the spaceframe construction used on previous sports racers like the Type 718 was too expensive and time consuming to built for what was basically a production car. What they did carry over from the 718 was the mid-engined layout, until then reserved solely to the marque's full blown racers. A combination of a steel ladder frame and a glass reinforced plastic (GRP) body was chosen. This was the start of a long line of 'plastic' bodied Porsche racers.
Responsible for the design of the GRP body was Ferry 'Butzi' Porsche, grandson of Ferdinand Porsche. He used some cues and the windscreen of the 718 Coupe and turned it into one of the best looking cars ever constructed. Production of the body was outsourced to airplane manufacturer Heinkel, who were able to produce two bodies per day, which was twice as fast as Porsche could produce the chassis. The body was bonded on the frame, which resulted in a chassis far more rigid than the spaceframe chassis used in the previous racers.
At the start of the project the engineers planned on using Porsche's all new two litre flat 6 engine, which was designed for the upcoming 901/911 model. Unfortunately, the engine's development was hampered and it was not ready yet in time for the 100 example production run. As a stop gap, the four cylinder engine from 356 Carrera 2 was uprated to produce 180 bhp in race trim. It retained the unique shaft driven overhead camshafts. Bolted directly on the 'old' engine was a new five speed gearbox, which was also developed for the new road car.
Three prototypes were constructed and tested heavily in the fall of 1963. After various modifications were carried through, the car was first shown to public late in November. Internally it was known as the '904', but it was marketed to the public as the 'Carrera GTS'. Today it's commonly referred to as the 904. Within two weeks all but 21 of the 90 examples available for the public were spoken for. Production started soon after in a completely new factory, constructed to produce the new 901/911 model. By April of 1964 enough examples were constructed to homologate the 904 as a GT.
Although it took until April for the cars to be homologated, the cars were already entered in various races. At Sebring the Lake Underwood and Briggs Cunningham driven 904 finished 9th overall and 1st in the prototype class. This was the start of a highly successful racing career, with overall victory in the Targa Florio and many class victories in races like the 24 Hours of Le Mans. Underlining the car's versatility was a second place finish in the snow covered 1965 Rallye Monte Carlo.
Throughout 1964 Porsche continued to develop the 904 and provided their customers with various new parts to keep the cars on the pace. Two of the works cars were fitted with a two litre version of the Formula 1 racers eight cylinder engine and later in the year the six cylinder engine finally made its introduction. These versions were not built in sufficient quantities to be homologated, so they raced in the prototype class only. Larger ducts for cooling the bigger rear brakes is an exterior feature of the 904/6. It was eventually replaced in 1966 by the 906 prototype racer.
Today the 904 or Carrera GTS remains as one of the finest and most successful Porsches ever constructed. It kickstarted a program of racing cars, that would eventually result in the all conquering 917. It also holds a unique spot in the manufacturer's history as the last dual-purpose sportscar Porsche ever built.
Chassis 906-001 was the very first six-cylinder engined Porsche sports racer. It combined the Porsche 904 chassis and body with the new type '901' flat six. It was one of over a dozen prototypes built in 1964 and 1965 that would ultimately lead to the 906 introduced in 1966. It debuted in October of 1963 at Montlhéry in the hands of Herbert Linger and Gerhard Mitter. Following extensive testing over the winter, it served as one of the works cars for the 1965 season. Among its many notable results are a third overall in the Targa Florio and a class win and fourth outright at Le Mans against cars with engines more than twice as big. The effort was also awarded with the coveted Index of Performance prize.
The car's final works outing came at the 1966 Targa Florio where it was used extensively during the training sessions by most of the Porsche works drivers. The scrutineering stickers from that event are still on the windshield. More recently, the car was meticulously restored by Gunnar Racing in the United States. The stunning result was awarded with a 'best in class' during the second Rennsport Reunion, in 2004. Chassis 906-001 was subsequently brought back to Europe where it was raced in the 2004 and 2006 Le Mans Classic in exactly the same configuration as it won its class back in 1965.
This the second Porsche 904/6 produced late in 1964. Having served primarily as a test and development car for the works team, it was sold to gentleman racer Michel Weber ahead of the 1966 season. In private hands, the six-cylinder engined Porsche was only briefly raced with a third at Hockenheim late in 1967 as the best result. Beautifully restored, the rare Porsche is now in Brazilian hands. It is seen here in action during the 2008 and 2009 editions of the Monterey Historic Automobile Races at Mazda Raceway Laguna Seca.
Built early in 1965, chassis 904-006 was the fourth 904 with the six cylinder engine and the familiar Ferdinand Porsche designed body. We do not know if it was raced by the works team in period but it did eventually surface in the United States through legendary dealer Vasek Polak. He entered the car for Milt Minter in select races during the 1968 with a victory at the Santa Barbara SCCA Regional as the best result. Today the Porsche 904/6 is owned by a noted American Porsche collector. He is seen here in action during the 2010 Le Mans Classic.
The penultimate Porsche 904/6 constructed, chassis was given select outings by the works team during the 1965. The best result was a second by Gerhardt Mitter during the Course de Cote hillclimb on the legendary Mont Ventoux. Subsequently sold to Vasek Polak, it was raced in SCCA events with a four cylinder engine for homologation reasons. During the 1980s, it was completely restored to its original configuration by Gunnar Racing. In the following years, the 904/6 has been extensively used and is seen here in action during recent outings at the 2009 Monterey Historics and the 2010 Le Mans Classic.
What a beautiful classic!
A perfect compromise between style, low weight and limited power for a very focused competition winning machine.
Thanks a lot for the great pictures and the detailed article about a car that I was ignoring before.
As italian, I am a Ferrari admirer, but personally I think that the "Porsche dinasty" gave the best optimized architectures to the car engineering world. Efficency Vs. Brute force.
What a nice brains competition!