The Mercedes-Benz R 107, 1971-1985

In spring 1971, another production sports car was presented with the Type 350 SL, replacing the 280 SL, which had been built since January 1968. Technically, this model was a brand new development which had almost nothing in common with its predecessor. However, the same basic components had already been used in other Mercedes-Benz models: Front and rear wheel suspension was basically the same as that of the " Stroke Eight" models and the V8-engine was a familiar feature of the saloons, coupés and convertibles of the 280 SE 3.5 Type.

With respect to the general concept the differences were less clear: Like its predecessor, the 350 SL was a two-seater with fully retractable roadster hood and removable hard top. However, the new model, represented a once and for all departure from the uncompromisingly hard sports car, - and, incidentally, even the "Pagoda SL", too, was not a true representation of that type - in favor of a more comfortable yet powerful luxury two-seater. The 350 SL - with the internal code name R 107 - was equipped with numerous innovative details, which were to result in increased passive and active safety and set the course for the future development of passenger cars. The fuel tank was no longer located in the rear of the car but had been transferred to a collision-proof position above the rear axle. In the passenger cabin, an upholstered dashboard, flexible or retractable switches and buttons and the new four-spoked steering wheel with an in-built rebounding device and a broader upholstered center-piece provided a maximum of safety in case of collision.

New wind deflector profiles at the A-pillars, which served as drainage rails for dirt water in heavy rain and kept the windows clean even in poor weather conditions guaranteed very good vision. Further details, adding to the safety of the car, were clearly visible indicators as well as large taillights, which, thanks to their ribbed surface profile, were almost completely soil-repellent.

Half a year after the launch of the 350 SL a sister model was presented at the Paris Motor Show; this was the Type 350 SLC, a four-seated coupé with fixed roof, which technically and stylistically, closely resembled the roadster, but had a wheelbase which was 360 mm longer. In April 1973, both models, roadster as well as coupé, had also become available with a 4.5-liter V8-engine with increased cubic capacity. A low-compression 195 hp version of this engine, which had been revised to comply with the US-legislation on emissions, had been available for exports since July 1971 and, with the North-American design of the 350 SLC, since July 1972.

In July 1974, the SL model range was again extended: following the oil crisis in 1973, roadster and SLC coupé were now available with the 2.8-liter dohc-injection engine, which had proven its worth for two years in the "Stroke Eight" series and the S-Class. This meant that the customer could now decide between three differently motorised SL models which is nothing unusual today but was a complete novelty in the history of that class then. Only an experienced observer was able to distinguish these models from each other; whereas the 280 SL had narrow tires, the 450 SL had an inconspicuous front spoiler, which was attached to the rear lower end of its front apron and served as an airing device for the radiator.

Between November 1975 and February 1976, all three engines were fitted with a new fuel injection system in order to comply with the stricter emission limits, which had been introduced in most European countries. The electronic injection control "D-Jetronic" by Bosch was replaced by a new mechanical "K-Jetronic", also by Bosch. This step led in all three cases to a certain loss of power; in the 2.8-liter and 3.5-liter engines, compression had been slightly reduced. In order to facilitate maintenance, the two new V8-engines were fitted with a breakerless transistor ignition system and hydraulic valve-clearance compensation. In the 2.8-liter unit, compression was increased to its former value in 1978; with the help of some ancillary measures the former driving performance was regained.

At the Geneva Motor Show in March 1980, an uprated version of the 107 series roadster and coupé was presented; the equipment of the interior including the steering wheel had been brought up to the standard of the S-Class saloons. The former 3-speed automatic transmission was replaced by a 4-speed version. Light-alloy engines of the S-Class were built into the 107 series models in slightly modified form.

The new Type 500 SL with its 5.0-liter V8-engine, which had been carried over from the 450 SLC 5.0 replaced the 450 SL. The 350 SL, too, was phased out after a production time of nine years; the 380 SL was the successor, with a 3.8-liter aluminum-alloy engine based on the old 3.5-liter V8 with a cast iron block. Only the six-cylinder engine of the 280 SLC was unchanged. There were hardly any external differences to the predecessor; all three SL types now had an aluminum bonnet and the 500 SL also had an aluminum boot lid with a black plastic rear spoiler.

In autumn 1981 both V8-engines were thoroughly modernized as part of the "Mercedes-Benz Energy Concept" for reducing consumption and emissions. This involved not only higher compression, but also camshafts with altered timing, improved injection valves and electronically controlled idling. The altered valve timing meant that maximum torque could be achieved at lower revolutions and was even increased for the 3.8-liter engine. This engine was changed the most. In order to achieve a more favorable volume to surface ratio the bore was reduced and the stroke increased. The modified 3.8-liter V8 thus arrived at a slightly higher capacity. In return for improved economy, slight drops in output had to be accepted; rear axle ratios were altered accordingly.

These modifications came too late for the SLC coupés, however. At the Frankfurt Motor Show in September 1981 their successors, the 380 SEC and the 500 SEC, were presented, but despite a production run of ten years there was still no end in sight for the SL models. Four years after the presentation of the energy concept the SL models were again thoroughly modernized and presented at the International Motor Show in Frankfurt in September 1985. There were minor external changes, improved front wheel suspension and above all, a new range of engines.