Mike De 'Udy and the Carrera
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www.porscheroadandrace.com Mike de ‘Udy and the Carrera Six Published: 24th November 2017 By: Kieron Fennelly Online version: https://www.porscheroadandrace.com/mike-de-udy-and-the-carrera-six/ The formidable Carrera 6 outside the Porsche headquarters, Stuttgart Zuffenhausen, 1966 The Carrera Six, as Porsche officially called the 906, was a radically different car from its predecessor, the 904 GTS. The 904 was a sleek glass fibre bodied racer penned by Butzi Porsche, and it took over as Porsche’s competition model following such illustrious forebears as the RS 718 and RS 61 which brought the Stuttgart manufacturer so many victories in the early sixties. The 904 would maintain this tradition, winning the 2-litre class www.porscheroadandrace.com in top level European and US races. But as a hill climber, in the 1965 season, it had to yield to the nimbler Ferrari Dino of Ludivico Scarfiotti. Hitherto something of a Porsche chasse gardée, the Alpine hill climbs, today largely forgotten, were until the early seventies, a major feature of the competition calendar. Famous ascents such as Mont Ventoux, Schauinsland and Ollon-Villars attracted bigger crowds even than Pike’s Peak today, and winning them mattered. A Porsche 904 Carrera GTS Coupé in 1963 outside the factory in Stuttgart Zuffenhausen Porsches were originally bred with mountain ascents in mind – sales of Gmünd built cars to well-heeled Swiss enthusiasts helped to pay for the move to Zuffenhausen in 1950. Hill climbs had become a key part of Porsche’s competition programme by the 1960s when Edgar Barth (father of Jürgen) gleaned three European mountain championships. So, half way through that 1965 season Porsche attempted a total redesign of its Bergspyder 904 to wrest supremacy from the Ferrari. www.porscheroadandrace.com Porsche 904s being assembled in the Race Department in 1963. The car has a ‘Carrera GTS’ badge on the rear fender, denoting a 4-cylinder engine The 904 had a fabricated steel ladder chassis, a rather lower cost option than the tubular spaceframe of earlier Zuffenhausen racers, but a necessary element of cheese paring forced on Porsche by the massive outlay it had already undertaken to buy out Reutter in 1963 and www.porscheroadandrace.com simultaneously invest in 911 production. The much revised Bergspyder had a tubular chassis and tiny 13-inch grand prix wheels acquired from Lotus. Weighing a mere 1100lbs the new car was developed from scratch between July and August 1965, but inclement weather for the rest of the hill climb season meant that a head-to-head with the Dino never came about. Ferrari won the championship on points accumulated earlier in the year. However, the rapid transformation of the 904 had taught Porsche lessons, no more so than to Ferdinand Piëch whose first racing challenge as Porsche’s new Technical director was the Carrera Six. The ambitious Piëch joined Porsche in 1962 and had been closely involved in engineering the 911 from the outset. A methodical graduate engineer, Piëch brought measurement and calculation to a Porsche which previously had relied on instinct and experience. The line of the 904 looked right to Butzi as had the final shape of the 901 (911), but the form of the 906 would be defined by the wind tunnel and would produce a less elegant but altogether more efficient body. The 906’s reduced frontal area, its rounded windscreen which created an almost aircraft like cockpit and its cut off (Kamm) tail were all the result of aerodynamic testing. A spaceframe required more machining and assembly but contributed a lighter and above all more rigid chassis and enabled bodywork sections to be unstressed and so lighter. The 906 would weigh 20% less than the 1500lb 904. www.porscheroadandrace.com Manufactured between 1965-1966, the Porsche 906 Carrera 6 was powered by a race tuned version of the 6-cylinder 911 engine (1991cc), and produced 210bhp For the 906’s running gear, Piëch was obliged to use components bought in anticipation of a second 904 production run which never took place. So, the front and rear axles had the same unequal length wishbones and coil spring arrangement though they did use the new Bilstein gas filled dampers instead of the 904’s Konis. If Piëch also had to give way on wheels, using standard 15-inch pressed steel five stud items instead of (much more expensive) centre nut jobs, he was keen to get the wider rubber which Dunlop, with whom Porsche was contracted, was offering. The 7-inch rims specified for the 906’s front axle and the 9-inch on the rear incidentally had the effect of disqualifying the Porsche Carrera Six from road registration in Germany where tyres had to have the same width back and front. As Porsche soon realised that at least 50 racing clients were likely to take the new Carrera, www.porscheroadandrace.com having to sell road going versions to make the homologation minimum became irrelevant. Interestingly, Zuffenhausen engineers also wanted the 911 to benefit from wider rear tyres too, but the German highway authority did not relent on this point until 1972, the 2.7 Carrera RS becoming the first road going Porsche with bigger back wheels than fronts. Le Mans 24 Hour, 20/21 June 1964: One of two 8-cylinder 904s in the race, this one driven by Porsche stalwarts Herbert Linge and Edgar Barth, waits in the pits before the start. The #29 Porsche 904/8 would retire with clutch problems With the exception of a handful of works flat-eights, the 904 GTS had used the Type 587 4- cam flat-four, but at 180bhp, the four had reached the limit of its development and Porsche was keen to exploit the potential of the 2-litre flat six. Raising the output of the stock 130bhp 911 unit to the Carrera Six’s 210bhp was no mean achievement. Though visually similar, the racing engine benefited from major reworking of its innards. Porsche drew www.porscheroadandrace.com heavily on its experience with the flat-eight engine of the 1962 F1 grand prix car, endowing the 906 with a far lighter magnesium (instead of aluminium) crankcase. The stock Solex carburettors of the 911 were swapped for a pair of triple-throated Weber type 46 IDAs (a modification later applied to the 911 range). A second plug hole was bored into each cylinder and this dual ignition system was presided over by a very precise, if fiddly to adjust, Marelli distributor. The cylinder head was machined and polished and fitted with larger inlet and exhaust valves to enhance breathing and the rocker arms were chrome hardened on their pressure points. Specially forged Mahle pistons with two compression rings and one oil ring operated in aluminium cylinders with hardened chrome bore surfaces, dimpled to retain oil. Le Mans 24 Hour, 19/20 June 1965: The German pairing of Herbert Linge and Peter Nöcker drove a solid race to bring their Porsche 904/6 home in fourth place overall www.porscheroadandrace.com Interestingly, the bottom end was almost that of the stock 911 using its 8-bearing crankshaft and oil pumps. But the 906 made significant use of titanium with the cylinder head bolts and connecting rods, fashioned in this exotic and (then) truly space-age metal. This contributed to the remarkable 119lb weight saving over the stock 911 engine. Karl Ludwigsen observes that the Carrera Six was in effect the first series production car in the world to employ titanium. The 906’s 5-speed gearbox shared its magnesium casing with a limited slip ZF differential. Porsche offered six different sets of ratios and three different final drives, giving customers plenty of options. Cleverly, cogs could be removed and inserted with the gearbox in situ, simply by taking off the rear plate. Competition history and significance The 906 had an auspicious start: the first car off the line in early January 1966 was dispatched to VW’s proving ground at Ehra Lessien where Peter Falk and Helmuth Bott thrashed it for 1000 kilometres over test surfaces, before bringing it to Weissach for suspension setting on Porsche’s new skid pan. A visit to the paint shop saw the Carrera Six turned out in a striking sky blue before it was packed off the Florida where it ran faultlessly to finish sixth (and first in the 2-litre class) at Daytona. The 906 looked amazingly low and petite next to the monster Ford GT40 Mark II which was then ruling the roost. At Sebring a month later, no fewer than five 906s started and the best placed (4th) finisher was loaned to Joe Buzzetta who proceeded to dominate the 1966 SCCA season where some of his closest races were against other 906s driven by competitors like Scooter Patrick. By mid-April the requisite fifty Carrera Sixes had been built and were running as Group 6 prototypes. A 906 provocatively beat Ferrari at the Monza 1000km and also chalked up Porsche’s sixth outright win in the Targa Florio. The 906 could only occasionally outrace the 400+ horsepower Fords or Ferrari 275LMs, but would reliably make six and seventh places in the main endurance races, a pattern which would continue in 1967. During this season, Porsche pioneered Bosch fuel injection on its works entries. This endowed 10 to 15 more bhp and gave a more linear throttle response. Three 906s were fitted with a longer tail for Le Mans which upped maximum speed as hoped, but at the expense of stability. Race car aerodynamics in the late sixties was very much a hit and miss affair, as the brave pilots of the first 917s would later discover.