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The First Eight-Cylinder – The 350 SL


In April 1971, a new Mercedes-Benz 350 SL hit the road – and conquered the customers' hearts straightaway. It was the first SL with an eight-cylinder engine under its elongated hood. Strong, self-assured, representative and masculine compared to its predecessor with its allegedly feminine touch, it presented itself as a well-proportioned roadster from all sides, with an equally well-designed, removable coupe roof.


The bodywork expressed not only elegance and quality but also safety – the open two-seater's crash behavior was far ahead of its time. Both axles rested on comfort-enhancing subframes, the rear assembly being a modern diagonal swing axle.



A memorable decision


After fierce debates, the Board of Management finally decided to produce the R 107 ( R for roadster ), as the 1971 SL was internally called, on June 18, 1968 . One of the crucial questions was whether the roadster should rather become a coupe with sunroof because alarming news concerning the safety – and type approval – of open-top cars had arrived from the USA : it was touch and go for them, and history has shown that they did, in the end, go.


The Board's decision in favor of a roadster with removable hardtop was therefore a fundamental, future-oriented decision, entirely owing to the then Chief Engineer, Dr. Hans Scherenberg, who had vehemently fought for this concept. "The SL gave me a lot of pleasure, but also a lot of trouble. It was not an easy job," he summarized that memorable meeting at a later stage.


The coupe remained an issue, of course. It was not decided upon on that day but talks were continued on the subject of whether an additional four-seater sports coupe should be designed on the basis of the R 107, or whether an "image coupe" should be launched at a much later point in time, towards the mid-seventies, on the basis of the future S-Class.


Karl Wilfert, head of bodywork design in Sindelfingen at the time, had developed a coupe on the basis of the R 107 somewhat high-handedly, and he did present the rough design to the Board of Management at some stage. It was rejected in the first instance but Wilfert, a man with perseverance, eventually succeeded in gaining acceptance for his idea of a sports coupe.


And so, just six months later, the new SL was followed by a comfortable four-seater sports coupe, the 350 SLC. Its independent design made a large number of friends anywhere in the world in the course of time. In terms of its exterior appearance, the SLC was virtually identical with the roadster up to the windshield – from there on, it displayed an elongated wedge shape. The four-seater passenger compartment was topped by a gently curving roof which flowed into a huge rear screen set at a steep angle and curved in two directions. Contrary to the roadster, the trunk lid had a slightly convex curvature.


Seen from the side, the car's length was demonstrated by a longer wheelbase – 2820 rather than 2460 millimeters – and by the lines of the side windows; as customary on Mercedes coupes, they were fully recessible and unmarred by B-pillars. The coupe's Cd value was clearly better than the roadster's so that it had the same performance in spite of being some 50 kilograms heavier.


62,888 buyers opted for the SLC in the course of its ten-year lifecycle. It is particularly remarkable that it fully lived up to its name, sports coupe, because it scored victory in numerous rallies and long-distance races throughout the world.



Roadster safety


Béla Barényi's safety concept with crumple zones front and rear and the rigid passenger cell – the three-box principle – was also incorporated in further developed quality in the 1971 SL. Unlike its predecessor, the R 107's backbone was not just a shortened and reinforced sedan floor but an independently designed frame/floor unit with an enclosed propeller shaft tunnel and box-shaped cross and side members, their special feature being different sheet metal gauges for deformation to a predefined pattern.


The SL was to be designed by all means as an open-top car without a Targa bar for appearances' sake, so the only safety features for the roadster in the event of a rollover were the A-pillars with the windshield between them. So these pillars were newly developed from the ground up to acquire a strength that was 50 percent higher than in the predecessor. The windshield was bonded to the frame to increase strength. This provided for a remarkable level of resistance in the roof drop test – which meant that the open-top car acquired the safety experts' approval in the USA even without a Targa bar. It goes without saying that the rear screen in the hardtop was also bonded in.


Ground-breaking innovations were also incorporated in the interior. The conventional – hard – dashboard was replaced by an ingeniously designed sheet metal construction: both the upper and knee-impact sections were foam-padded and yielded on impact. Another new feature was the four-spoke steering wheel, designed on the basis of the accident researchers' latest findings. It still incorporated the proven impact absorber but now had rim, spokes and boss padded with polyurethane foam. ABS became optionally available in March 1980, airbag and belt tensioner in January 1982.



A bestseller right from the start


Nevertheless, customers all over the world did not rush to the showrooms to order the new SL with safety in mind. They were attracted by the offer of a perfectly balanced open-top car – the only one of its kind built for years to come and attractive for that reason alone. Its distinctive front end with a dominant SL face, broad-band headlamps and ribbed turn signal lenses gave the car a powerful appearance; the low silhouette featured harmonious lines no matter whether the car was open, closed or fitted with its hardtop, and the slightly concave trunk lid was reminiscent of the Pagoda era. Ribbed, dirt-deflecting broad-band rear lights gave the rear end a strong, masculine touch.


The "fastest" soft-top of all cabriolets and roadsters – a further refined design of the Pagoda version – was highly conducive to comfort and ease of operation: the process of opening or closing took a mere 30 seconds. As customary in SL roadsters by then, the soft-top vanished under a cover when folded down.


From the start of production, the 1971 SL boasted the 3.5 liter eight-cylinder engine which had celebrated its premiere in the 280 SE 3.5 coupe and cabriolet in 1969 and had since been praised to the skies. Its 200 hp at 5800 rpm helped the SL – which weighed as much as 1600 kilograms – to accelerate from standstill to 100 km/h in nine seconds. Its top speed: 212 km/h.


A number of detail features turned life in and with this car into a pleasurable experience. Right from the start, the seats were fitted with head restraints and seat belts. A highly responsive heating and novel air channeling in the area of the doors enhanced well-being and physiological safety. Dirt-deflecting moldings on the A-pillars and exterior mirrors enhanced visibility in poor weather. The windshield wipers, centrally arranged close to each other, swept a remarkable 70 percent of the windshield, were aerodynamically efficient and did not lift off at high speeds.



Engines with catalytic converters


Nobody had foreseen that this SL would remain in production for 18 – highly successful – years. During its lifecycle, a large number of six- and eight-cylinder engines were used, with correspondingly diversified designations for the relevant model versions.


The 280 SL with 185 hp from 1974 until 1985 and the 300 SL from 1985, with 188 hp without and 180 hp with catalytic converter, belonged to the successful six-cylinder lineup. They had virtually the same high performance as the smaller eight-cylinder models but were less expensive and less thirsty.


The first of the eight-cylinder engines was the 200 hp unit in the 350 SL produced from 1971 until 1980. Its larger brother available at the same time, the 450 SL, was blessed with 225 hp. The 500 SL with 240 hp followed in 1980; its engine was completely revised, made of aluminum and combined with a catalytic converter in 1985; it developed 245 hp thereafter and remained on offer – with clearly more moderate drinking habits – until the discontinuation of production in 1989. In 1985, the 450 was replaced by a new 420 SL which developed 218 hp without and 204 hp with catalytic converter. A somewhat exotic model was the 560 SL which was only offered in the US market – with an American catalytic converter and an output of 230 hp.


237,287 roadsters were produced in the course of 18 years. The hardtop was included in the standard specifications in March 1980.


The roadsters and coupes of the R/C 107 series continued the legend as both comfortable tourers and indestructible sports cars. The attraction of the magical letters, SL, remained undiminished, as underscored by 300,175 automotive building blocks of a legend, produced in the course of 18 years.



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