Despite not being produced entirely as it was conceived, the Porsche 904 proved to be a versatile competition car
Almost by tradition, Porsche's sports racing cars were built with tubular frames. Hermann Ramelow designed the original tubular frame Porsche, the type 550, which first raced in 1953, as a complete departure from the type 356 production cars which were far too compromised to remain at the forefront in racing, especially with their overhung rear engines.
In 1964, though, Porsche made a surprising conversion back to a platform chassis construction for the type 904, the sports Grand Touring model which achieved a great many successes in racing, even in rallying, in various parts of the world.
Porsche's Formula 1 programme was brought to a close at the end of 1962 with a single success for Dan Gurney in the French Grand Prix at Rouen, and since the company was in one of its periodic downturns company chairman Dr Ferry Porsche decided to concentrate on production-based cars for competitions.
He intended the new six-cylinder engine, designated 901, to power the type 904 racing car when it was launched for the 1964 season. This was almost a year before the new production model, the 911, went into production, and it was eventually decided to stay with the Fuhrmann designed four-cylinder, quad-cam engine.
Both engines developed approximately 180 horsepower, but there were plenty of four-cylinder units in service around the world and all the potential customers at least 100 of them, since that many cars had to be produced for GT homologation had plenty of experience of them.
Expensive as they were, and a nightmare to rebuild it required 100 hours of labour to take a Fuhrmann engine apart and put it together again), the four-cylinder engine was a well proven component.
The new 'six' was just too new to release on a worldwide basis, especially in tuned-up form with I 80 bhp, the same level as the previous year's 1.5-litre, eight-cylinder F1 engine.
There was ample space in the engine bay for the four-cylinder engine, enough for the six-cylinder, and for Porsche's eight-cylinder racing engine.
The intention was to build 100 examples with the four-cylinder engine and homologate these as GT cars, and to make a small series for Porsche's own team with six and eight cylinder engines.
Then, a second series of 100 would be made for the 1965 season entirely with six-cylinder engines, with an evolution certificate for GT competitions.
The 904 was never developed as planned, though, and the second series was never made. Records show that 104 cars were made and sold with four-cylinder engines and of the remaining 16, retained by the factory, 10 had six-cylinder engines and six had eight-cylinder, two-litre engines derived from the 1.5-litre Formula 1 unit.
The suspension components were similar to those on the previous year's 804 Formula 1 racing car, though productionised, with a double wishbone front suspension and a complicated four-link rear suspension.
Telescopic shock absorbers and coil springs were featured, with no sight of Porsche's more familiar torsion bar system.
Ing Hans Tomala, who developed the 901 power unit, was appointed to supervise the design of the 904. Ing Schroeder designed the simple boxframe steel chassis, which had little torsional strength without the rollover bar and glass-fibre body, and the 904 was styled by Ferdinand 'Butzi' Porsche, who had only just signed-off the 911's timeless bodystyle.
In Porsche's parlance Tomala was the 'father' of the design, an excellent system whereby one man is responsible for the quality arid integrity of the design, the costing, the ordering of special parts, and the timetable.
The price quoted by the 904 Carrera GT was very attractive at DM 27,900 (about £2800 at the prevailing rate of exchange). In standard form the 904 GT had 51x15 pressed steel wheels and a proper exhaust system which reduced the power to 155 bhp at 6400 rpm, ample for a car that weighed only 650 kg.
The 904 never went near a wind tunnel but it looked very slippery, with its headlamps recessed far back behind perspex shields. It proved to be a versatile machine which was far from ideal for road use ("normal conversation is utterly impossible at 100 mph" remarked Car & Driver, "the owner/driver would have to be slightly out of his mind to use it on the highway"), but it was loved to death by the lucky customers.
The road version had a top speed of 160 mph, accelerated to 60 mph in 5.3s and to 100 in 12.2. The 904 was without doubt one of the world's fastest GT cars, never mind that it had a small, Weber carburated engine with none of the glamour of a Ferrari V6 or V12.
No figures were recorded for the competitions model, the GTS, which developed 180 bhp at 7200 rpm, but they put the 904 GTS at the top of the two-litre division. Apart from the many racing successes, the most amazing exploit was Eugen Bohringer's drive to second place overall in the Monte Carlo Rally in 1965, the snow-bound event won by Timo Makinen in a works Mini Cooper S.
So unsuitable was the 904 for this type of event that Bohringer's second place must rank alongside Juan Manuel Fangio's victory in the 1957 German Grand Prix.
And three places behind, to Porsche's great delight, was the new 911 making its competition debut in the hands of Weissach engineers Herbert Linge and Peter Falk.
But I have jumped a year! The 904 model may not have had the new six-cylinder engine as yet, but it did incorporate its five-speed gearbox, its ZF rack and pinion steering, its Dunlop-ATE four-wheel disc brake system and many more items, all pre-production parts which saved money and accelerated the durability trials.
Early photos showed clean bodywork behind the doors, but the rear brakes were soon found to overheat. The 904 GT soon featured an air inlet grille, while the GTS had prominent air scoops forcing cold air to the brakes.
Development of the 904 was completed in the space of six months, confined mostly to the Nurburgring and the skid pan at Weissach, the site of Porsche's new research and development centre.
Two 904s made their debut at Sebring in March 1964, running as prototypes since the run of 100 hadn't been completed. Herbert Linge and Edgar Barth encountered clutch problems and finished 20th, while Briggs Cunningham and Lake Underwood had a clear run and finished ninth, winning the two-litre division.
A month later, and duly homologated, Porsche 904s were the surprising claimants to first and second places overall in the Targa Florio. As faster cars broke or crashed, Colin Davis and Antonio Pucci drove for a win followed by Herbert Linge and Gianni Balzarini.
The 904 had not been considered as an outright winner, certainly not in GT form with the four-cylinder engine, but it was a supremely reliable machine which fairly dominated the two-litre GT category.
All five cars entered at Le Mans finished safely, that of Guy Ligier and Robert Bouchet finishing seventh overall, and at Reims all eight Porsche 904s reached the finish. Later in the season Barth and Davis drove an eight-cylinder, 235 bhp Porsche 904 to third place in the Paris 1000 km behind a pair of 3.3-litre Ferraris, and this set the tone for 1965.
Ing Tomala left the company and was replaced by Ing Ferdinand Piech, Ferry's nephew. Piech had considerable flair and forced the pace of development. One of his first decisions was to produce a new racing car, reverting to a tubular frame, for the 1966 season. This would be called the 906, and in the meantime the 904 came to be regarded as a stopgap model which competed in a variety of forms.
At the 1965 Targa Florio, for instance, four different types of 904 pursued the winning Ferrari. Colin Davis and Gerhard Mitter finished second in a unique 904 Spyder powered by the eight-cylinder engine (it had been rejected by Io Bonnier as being insufficiently rigid, which was undoubtedly true).
They were followed by Herbert Linge and Umberto Maglioli in the 210 bhp, six-cylinder 904 and by Bonnier and Graham Hill in the eight-cylinder 904 coupe. Fifth overall, and winners of the GT categorywere Gunther Klass and Antonio Pucci in a 185 bhp 904 GTS.
The 904's durability proved itself again at Le Mans where Linge and Peter Nocker took fourth place overall in a six-cylinder 904, behind three Ferraris. Linge, the factorys test driver, had a special 901 engine made of magnesium instead of aluminium alloy, saving valuable weight, and this became the basis of the 911's engine in 1969.
Everything that came out of Weissach had a purpose, and this is as true today as it was then.