The Porsche Carrera GTS represented a watershed in the company’s march towards motorsport fulfilment. Gone was the space frame and aluminium construction of the 550s, the Type 904 ushered in a completely new way of thinking. Porsche Road & Race investigates…
The Porsche Carrera GTS, or Type 904 to give it its internal company designation, marked the biggest change in direction in Porsche’s motor sport philosophy up to that point and for the next two decades, until the introduction of the 956 in 1982. Increased competition from Alfa and the Fiat Abarths in the FIA 2-litre GT class in the early 1960s, is seen as the inspiration for a new race car, in what Porsche regarded as its domain.
To unpack this statement, we need to take a brief look at what had gone before. The earliest Porsche racers were none other than aluminium bodied 356s, and these were followed by the 550s when the company decided to construct a purpose-built race car. The 550-family evolved through many different versions, culminating in the 718 GTR Coupe (1962) and the 356 B 2000 GS-GT Coupe (1963) or Dreikantschaber as this latter model was also known. In profile, these two models looked quite similar although they were powered by different engines, the former by an 8-cylinder engine and the latter by a 2-litre 4-cylinder engine. The model name ‘356 B 2000 GS-GT Coupe’ is a bit misleading because it looked nothing like a 356, but it shared the same 2100mm wheelbase, being shorter than the 718’s 2300mm wheelbase.
While the 718 GTR and the Dreikantschaber may have shared a similar silhouette, they were not graceful in appearance, as the name might suggest (Dreikantschaber – this literally means three-sided scraper). Having said that, the front end of both models clearly pointed to its successor, which resulted in what many regard as one of the best Porsche race car designs ever, the Type 904. But it is not just the new car’s design and overall shape that set it apart, it was the overall construction of the car that was revolutionary for Porsche. The 904 used a box-section steel frame construction, to which was attached its fibre glass body, this being a first for the Stuttgart company.
In order to free up the much-needed resources for this innovative project, Ferry Porsche pulled the plug on the development its Type 804-F1 Monoposto. The company reasoned that they would earn back their investment in this new Type 904 project through the sales of the Carrera GTS, while their Formula 1 cars were not sold, but merely generated exposure for the company.
The rules governing the 2-litre GT class, in which the 904 was eligible, required that 100 cars be produced to meet homologation requirements. Porsche did not anticipate having 100 racing customers lining up to buy the 904, and they certainly could not afford to have this quantity of unsold cars sitting around. For this reason, the 904 was offered for sale at just DM29,700 (£2673 or $7481 at 1963 average exchange rate). In order to meet the homologation requirements as a GT car, it had to have a passenger seat and a nominal luggage compartment, and with roadgoing customers in mind, it featured a heater and an adjustable steering wheel. History shows us though, that Porsche has over the years erred heavily on the side of caution when it came to estimating the potential market size for their cars. This was the case too with the 904, as no sooner were the original 100 units allocated than an additional 20 cars were also produced, although a few cars were not assembled, but were kept as spares.
At the time of the 904’s design, Porsche had not had any experience in the field of fibre glass body manufacture, and so with speed of production at the forefront of their minds, the race department turned to the aircraft manufacturer, Heinkel. The aircraft manufacturer was able to assemble complete bodies, which comprised fifty separate body parts, at the rate of two a day while Porsche could produce only one chassis per day which meant that Porsche really had to strive to keep up the production rate. The completed chassis were despatched to Heinkel who bonded the fibre glass bodies to the steel chassis, and then returned the assembly to Porsche. This process significantly strengthened the overall rigidity of the 904’s body and chassis.
A fibre glass construction method was specified for three main reasons, the first being one of cost, because making fibre glass body panels was relatively cheap when compared with steel or aluminium. The second was speed of manufacture, as several of the same body panels could be produced at the same time while the third reason was one of weight, as fibre glass was much lighter even than aluminium.
The engine was mounted ahead of the rear axle with the gearbox over the axle, and the whole rear body panel (almost half of the car!) would hinge rearwards. The 904’s styling reflected the trend in the sport at that time, with the chopped off Kamm tail, and a door cut line that reached up onto the horizontal roof section, thereby creating easy access to the cockpit. One advantage for designer Ferdinand Alexander ‘Butzi’ Porsche, was that creating complex curves and shapes in fibre glass was far easier than trying to get this hand-beaten out of aluminium.
Development of the 904 began in early 1963 and it had been the intention to fit the 904 with the new 2-litre 6-cylinder engine as used in the new 901/911. Although the new 901/911 was launched at the Frankfurt Motor Show in the autumn of 1963 with the new 2-litre 6-cylinder engine, by the time the 904 was ready, this engine was certainly not ready for competition work. It was therefore necessary to fit the 4-cylinder Type 587 engine of 1966cc capacity which developed 180bhp at 7800rpm in race trim. This engine was a development of the original Type 547 4-cam unit (1953) that was designed by Ernst Fuhrmann, and which had powered the 550 Spyders to such success. Despite being a ten-year old engine, it meant that both spares and expertise were in abundant supply, at least as far as racing engines go, which was important for Porsche’s racing customers.
Of course the 4-cylinder engine was turned around 180 degrees, so that the engine sat ahead of the rear axle with the behind the axle. This was the same as in the earlier 550 series racers, but the opposite to the 356 cars where the engine hung over the back axle. The 904 was given an all-new 5-speed gearbox which featured a heavily ribbed, rigid tunnel case.
Three 904s were prepared for testing which began at the company’s test track at Weissach in August 1963, and this continued until the development freeze late in November. The 904 showed excellent stability in crosswind conditions, even at high speeds, which would give the driver additional confidence. At this stage the 904 was prepared for its first race, the Sebring 12-Hour race on 21 March 1964. No fewer than five of the new cars were on the entry list, but the only one to finish was the Lake Underwood/Briggs Cunningham car. Because Porsche had not yet been granted homologation for the 904, they were entered in the Prototype GT 3000 class where the #37 car (chassis 904 018) won its class and finished ninth overall.
The nimbleness of the 904 was clearly evident when at the Targa Florio on 26 April 1964, they made a clean sweep of the opposition by finishing first and second overall. Briton Colin Davis even set the fastest lap, and this in a car with a 2-litre 4-cylinder engine. Finishing in sixth place was the 904/8 of Edgar Barth/Umberto Maglioli, this car being fitted with a 2-litre 8-cylinder engine.
Homologation requirements meant that at least 100 units of the 904 had to be made within a twelve-month period, but in fact 118 were made. If Ferdinand Piëch had had his way, it would have been in the order of 200 cars, but the second batch of 100 cars was cancelled and so Piëch moved on to his next project, the 906, which was to replace the 904. In preparation for the second batch of 904s, complete sets of brakes and suspension components had already been ordered and received. Piëch, however, wanted to abandon the surplus suspension and brake components he had ordered for the 904 in favour of improved parts, but his uncle, Dr. Ferry Porsche, overruled him in a display of authority.
Of the 118 Type 904 cars produced, 109 were fitted with the Type 587/3 engine, a more highly tuned version of the 2-litre 4-cam Fuhrmann engine that produced 180bhp. Just six cars were fitted with the Type 901 6-cylinder engine that had been originally intended for the 904. Only three cars were fitted with the Type 771 2-litre 8-cylinder engine. To confuse matters, the 904/6 cars were given the chassis prefix ‘906’ while all the 4-cylinder and 8-cylinder cars retained the ‘904’ chassis prefix. In competition, the 4-cylinder engine proved to be extremely reliable, the 6-cylinder engine perhaps lacked sufficient development time, while the 8-cylinder engine was not that successful.
With the exception of the Targa Florio where it had an advantage over the heavier cars, the 904 was undoubtedly a threat to the prototypes wherever it raced in international competition. Looking at the results achieved by the 904 in 1964 in events like the Spa 500km, Nürburgring 1000km, Reims 12-Hours and the Paris 1000km, final positions usually ranged between third and fifth overall. This is a highly commendable record, as it was more often than not a batch of Ferrari 250 GTOs ahead of the Porsche. At the 1964 Le Mans 24-Hour race, a pair of 904s finished in seventh and eighth places, behind prototypes and much larger engined cars. Where it competed in the 2-litre GT class at events such as the Monza Coppa Inter-Europa and the Bridgehampton 500km, the 904s were in a class of their own taking the first five places in the former, and the first two places in the latter race.
In 1965, the 904 finished fifth in both the Daytona 2000km and the Sebring 12-Hour races, and fourth at the Monza 1000km behind three prototypes, two Ferraris and a Ford GT40. In the Targa Florio, a 904/8 Bergspyder finished second to a Ferrari 275 P2, and three more 904s followed in positions three to five. In the Spa 500km a 904 finished third and another also finished third in the Nürburgring 1000km, and amazingly in the Le Mans 24-Hour that year, two 904s finished in fourth and fifth place. To end off the season, Bridgehampton was again a success story for the 904.
This run of successful results just served to fuel the flames of ambition within Ferdinand Piëch, and it wasn’t long before the Type 906 broke cover. Where the 904 was a thinly disguised dual road/race car, the 906 was pure race, and opened up another whole chapter in Porsche’s illustrious motorsport heritage. Much had been learned from the 904, and the 906 made its debut at the 1966 Daytona in February, but more of that next time…
Words by Glen Smale
Photos by Porsche Archive