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 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.
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.
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 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.
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, 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.
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 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.
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.
The flat-eight version, bored out to 2195cc, delivered 250bhp and was tried in some 1967 906 works cars, but proved relatively fragile. By mid-season Porsche was already working on the 3-litre flat-eight which, in the new 908 model, would move Porsche up a capacity class in 1968 and create a race winner that would endure until the mid-seventies. Observing the Stateside success of the 906, Californian Porsche specialist Vasek Polak had the foresight to buy up spares and parts from Zuffenhausen once the Carrera Six had gone out of production and this helped to keep the sizeable US flotilla of privately owned examples competitive for several more seasons.
After two decades of being the king minnows, Piëch was leading Porsche against the big fish of sports car racing. The spaceframe 906 fired up the intense development programme which, within three years, would see Porsche produce the astonishing 917 and which, by the time its career was terminated by the rulebook, had become the most successful sports racer in history.
Mike de ‘Udy’s Carrera Six (chassis #906-129)
Jerry Pantis, author of Porsche 904, 906 and 910 in the Americas, reckons that most of the 65 906s made are still in existence, but after so many seasons’ competition, it is doubtful whether many retain much of their 1966/7 originality. However, the rise of vintage racing in the last two decades has been an incentive to restore old racers as sympathetically and originally as possible. In the case of 906-129, it means that almost ten years after its rebuild by Thomas Vintage Cars of Denver, Colorado, this 906 is about as good a representative of the classic 906 as you are likely to find. This is largely due to its being more or less laid up for 25 years from the end of its competitive racing career in the early 70s, and never subject to the more radical ‘improvements’ of private owners.
Mike de ‘Udy was a wealthy young London-based South African, a sort of latter day ‘gentleman racer’ whose enthusiasm frequently exceeded his talent. He was one of a number of drivers who drove the British importer AFN’s 906, chassis #101 (legally registered for the road LJJ 16D) in European events in 1966-67.
Several well-known ‘names’ were hired to race this car for AFN during the period including David Piper, Peter de Klerk and Tony Dean. Crashes were not infrequent, #101 coming to grief in the Targa Florio with de ‘Udy at the wheel. De ‘Udy said later he had been driving too fast because he was “pissed off” by being delayed at the start. He later crashed a 906 at the Kyalami 9 Hour race in November 1966, this time driving probably his own 906 chassis #129 which he had purchased earlier in the year. The 906 was not the first Porsche he had bought from AFN who had supplied the South African with a 904 GTS a couple of years previously. After the Kyalami accident, de ‘Udy had his Carrera Six repainted in the pale green colours of his Bahamas racing team. That winter he went on to score a second at the Pietermaritzburg 3 Hour race and a third at Cape Town’s Killarney, but the subsequent and far more competitive European season with 906s was patchy. Retirements at Spa, Zeltweg (where the rather wild de ‘Udy spun off) and Mugello where he shared a car with David Piper, were partly offset for entrant AFN by a thirteenth place overall (and second in class) in the BOAC 1000km race at Brands Hatch. There, chassis #101 was driven by the Swiss pairing of Dieter Spoerry and Rico Steinemann, the latter was to later become Porsche’s PR manager.
De ‘Udy persevered with his own 906-129 during the 1968 season, but by this time had become more interested in racing the immensely powerful Eric Broadley-designed Lola T70. So, in 1969 de ‘Udy asked his friend and sometime mechanic Bob Ridgard (who today makes the classic racing seats) to sell the Carrera Six for him. Ridgard, at that time, had found a market for used racing cars amongst US enthusiasts. The buyer of de ‘Udy’s 906 was a New Yorker, Carl Armstrong, who paid £3800 (around $9100) for the car. He and his brother, and later pal Tom Richmond, campaigned the Porsche in SCCA events until 1974 by which time it was becoming less competitive. Sold again, chassis #129 went to Bruce Tuffli of St Louis who paid $11,500 for what he described as a “cool car.” Former graphic designer Tuffli spent some years restoring the 906 which had finished its racing career in rather battered and unloved condition. The headlight Perspex had been crudely replaced by glass fibre and the internal headlight seating damaged; the scarred body carried the advertising decals of the previous owner’s company, and the roof panel had been lost and replaced again by a rudimentary hoop. The doors were cut down and windowless, and the Perspex engine cover was missing. It was altogether a sorry sight, Tuffli admitted. As part of his very long and largely single-handed refurbishment, he even carpeted the interior, intending to make the 906 ‘streetable’, a venture he finally decided was impractical, and he ended up garaging the Porsche for around 15 years.
This hibernation saved the 906 from further indignities. In 1998 Tuffli finally sold it on: “I wasn’t doing anything with it and I wanted it to have a good home.” He found one in the form of established classic racer Terry Hefty of Denver who consigned the mothballed 906 to Thomas Vintage Cars for a detailed restoration. The engine had seized through lack of use though was readily resuscitated and proved the least of the problems. Tom Ellis of Vintage explains that he worked painstakingly with the car, deciding not to remove the (original) body work as previous owners had glued it to the frame to make the structure more rigid, rendering removal impossible without damaging the glass fibre of what he could see was clearly a remarkably original 906. Vintage replaced the roof with the correct item and this allowed the gull-wing doors to be re-hung properly. The interior was restored to its 1960s look as far as possible, with a pair of period competition seats and six-point harnesses.
Hefty, though, was under the impression he had purchased chassis 906-101, as Tuffli had also believed 24 years earlier, as a letter from Jürgen Barth to him in 1975 stating that his car was “probably chassis #101 sold to AFN on 1 January 1966,” suggested. Terry Hefty discovered though that chassis #101 was attributed to a 906 now living in France (and its owner was not at all pleased to have the pedigree of his 906 questioned!) Hefty then understood that he must have chassis #129, a conclusion reached by Jerry Pantis whom Hefty had asked to look into the affair. The problem was, as Bruce Tuffli points out, that at some point, quite possibly after the car was repaired following the Kyalami shunt, the chassis identification plate was not put back and the car subsequently ‘confused’ with the other 906 driven by de ‘Udy, AFN’s #101, itself being sold on after the 1967 season. Bob Ridgard explains that the market for second hand race cars in those days was quite casual: nobody bothered about chassis numbers or correct provenance – old racing cars were just sold on, or worse, broken up after a season or two. After a couple of metal fatigue related accidents in 1968, Porsche often as not sold its competition cars straight after a race. Cash changed hands and that was about the sum of the formalities. Records of such transactions, if kept, were to say the least, thin. Little wonder that Barth’s letter to Tuffli is hedged with “probably.”
Terry Hefty found he was uncomfortable with the 906’s almost totally reclined driving position and hated the intimidating lack of rear vision. He raced the car only a couple of times after its restoration, selling it in 2006 to British Porsche enthusiast and hill climber, Paul Howells, well known for his collection of competition RSRs and other hot air-cooled 911s. The high point of Howells’ five-year tenure of the 906 was fourth place in the 2-litre class at the 2008 Le Mans Classic. In 2010 Howells sold 906-129 to the classic dealer Duncan Hamilton Ltd, fifty miles west of London, who maintained it on behalf of a private, London-based owner.
Driving impressions of Carrera Six #129
At just thirty-eight and a half inches high, even by Porsche standards, the 906 is extraordinarily low. It is neat in that sparing Zuffenhausen way, and looks extremely purposeful. Resplendent in a dark green which could be referred to as British Racing Green, though this has never been a defined shade, the 906’s bodywork is not perfect, showing entirely convincing ripples and creases here and there, as we all tend to have after nearly five decades! The exposed screws attaching the engine cover and the sheer functionality of the way everything is held together, show just how simply race cars were in the 1960s. The gull-wing doors weigh next to nothing, but opening them from inside is precarious as they slide all too easily out of their Heath Robinson slots in the roof. Temperamental Italian super cars of old were always said to need a mechanic in the trunk. With the Carrera Six, you could almost employ him full time to lift the door off so you can climb in and out, itself a minor act of contortion. No wonder Bruce Tuffli gave up trying to make this a street car.
The interior is convincingly period, thanks to the patina of several years’ use since restoration. The seats are slightly grubby, the bare floor scuffed and the only cabin addition is an eyeball air vent directed towards the driver. But this is a period item too and looks entirely in keeping. Three toggle switches control ignition and the turn indicator completes what is a purely functional environment. The car gets regular exercise in the hands of Doug Mitchell who looks after the Porsche at Duncan Hamilton and it fires easily, settling to a raucous 1200rpm idle. The clutch, which is hard against the steering column, has to be depressed right to the floor before a gear can be engaged, but then take-up is smooth. The driver is all but horizontal in a 906 and the nearness to the ground is intimidating at first, especially as the hull bottoms on the slightest unevenness. Out on the highway, the 906 is clearly an uncompromising competition car. There is almost no insulation from mechanical process: you are acutely aware of engine, gearbox and at low speeds you can hear the brakes too.
With only 600lbs over front axle, steering is light and very precise though the lock is very limited, another reminder that it was designed for circuits and not streets. Rear visibility in the 906 is very difficult and the open exhausts of #129 attract a lot of negative attention, but after a while at the wheel you start to build up a rhythm, urged on by that flat-six which is slowly warming up. For such a highly-tuned unit, it is remarkably tolerant of lower revs and the car is so light that the absence of proper torque down here is hardly noticeable. But at 4000rpm, you can feel the cavalry massing and from 5000rpm, acceleration is stupendous (as well it might be with around 400bhp/ton!) and we really need a circuit to go exploring beyond here. Cabin noise is prodigious: Ludwigsen reports that Hans Herrmann used to say he couldn’t hear anything till Tuesday after he’d raced the 906 on Sunday. The Perspex bubble of a roof too attracts the fall sunshine and heats occupants uncomfortably. We are very conscious too that this is half a million dollars of race car and reluctantly call a halt after forty minutes or so, reflecting that racing drivers of old were really heroes to hold these machines at the limit hour after hour.
The ex-Mike de ‘Udy Carrera Six #129 is a fine example of the 906, a classic Porsche customer race car. Like most of the privately owned 906s, its early competition record is nothing special, but #129 has at least a solid traceable history and also the merit of its original ZF gearbox and an original Carrera Six engine, (not the original which de Udy characteristically managed to break, but a fuel-injected unit from the 906’s second season). Chassis #129 has moreover a largely original chassis and body. Thanks to many years of storage followed by a sympathetic restoration, it not only looks the part, but performs as it should, as its Le Mans Classic performance showed. Porsches always go best when driven regularly (and properly)! Our thanks to the owner and to Adrian Hamilton and Doug Mitchell of Duncan Hamilton Ltd, for their advice and assistance.
Editor’s note – Paul Howells recalls
“I owned and raced #906-129, the ex-Mike de ‘Udy car, for five years. It was great fun to drive, but dangerous to race properly by today’s standards of safety, because it just had a lightweight tube frame that left you with exposed feet, and you had a fuel tank either side of you! The top of the left fuel tank even had a cut out for Mike’s cigarettes and a rag! I was clocked through the speed trap at night in the 2008 Le Mans Classic at 158mph. We finished the Le Mans Classic in fourth place on my first time at Le Mans. The car ran well apart from wearing one of the fuel tank straps through on the curbs of Le Mans in the last race. They were fragile cars that vibrated themselves to pieces if you did not keep on top of them. You could see the screws in the rear Plexi-glass turning in the rear-view mirror while driving flat out down the Mulsanne Straight! It’s the only race car I have owned into which I fitted a double fire extinguisher system – that says it all!”
Written by: Kieron Fennelly
Images by: Virtual Motorpix/Glen Smale & Porsche Werkfoto