When the Benz becomes the Koenig

Valley [ENA] Mercedes-Benz has produced around 74,000 coupés of the C126 coupé variant of the W126 series, which was unveiled at the IAA in 1981. This series, launched in 1979, set new standards in the luxury car segment throughout its long production run of 12 years. Yet its launch was met with criticism: some claimed that the ‘plastic age’ was beginning at Mercedes. Its predecessor, the W116 – occasionally dubbed the ‘chrome battleship’ – was one of, if not the, ultimate state limousine. Now, Mercedes’ chief designer Bruno Sacco had sketched a sober, aerodynamically streamlined body. The chrome bumpers had to make way for polyurethane ones. By the time production ended in 1992, just under 900,000 W126s had been built, securing the model range’s status as the world’s most successful luxury saloon of all time – a title it still holds today.

‘SEC’ became the model designation for the coupé, standing for ‘S-Class Injection Engine Coupé’. The underbody, derived from the saloon, was shortened by 85 millimetres, whilst the wheelbase was increased by 30 millimetres compared with the previous model. To maintain the saloon’s safety standards and due to the absence of B-pillars, the roof structure was improved and high-strength tubes were welded into the A-pillars. A number of design differences made the coupé unmistakable: narrower main headlights and fog lights integrated into the bumper allowed for a wide radiator grille that was incorporated into the bonnet;

this was no longer adorned by a freestanding star, but by a large star emblem set within the grille itself. Further design features on the sides and at the rear made the car instantly recognisable. As was customary with Mercedes, the coupé was positioned above the saloon in the range, was better equipped, powered exclusively by V8 engines and was therefore more expensive.

The car

The car described here was delivered in November 1985 as a black C126 series 500 SEC with a ‘Dattel’ leather interior. The M117 E50 series V8 engine delivered 231 PS (170 kW) at 4,750 U7min. The maximum torque of 400 Nm was available at 3,000 rpm. Power was transmitted to the rear axle via a four-speed automatic gearbox, enabling the car to accelerate from 0 to 100 km/h in 8 seconds and reach a top speed of 225 km/h The car undertook a 40-year journey from Stuttgart via Canada to the USA and eventually found an owner in Florida, who had the car registered under an ‘Antique’ number plate. The American owner had been a fan of Koenig cars since his youth, and this had given rise to the desire to convert his 500 SEC into a "Koenig"

Koenig Specials

The tuning firm Koenig Specials GmbH was, and remains, a German tuning company based in Munich, which specialised in modifying European luxury cars and was particularly well known in the 1980s and 1990s for its performance upgrades to Ferraris, as well as to Porsches and Mercedes-Benz cars. The founder, Willy König (known in English as Willy Koenig), born in 1938, was originally a publisher and, around 1961, an amateur racing driver in a Formula Junior Cooper purchased by Wolfgang von Trips. Under the pseudonym Robert Frank, he won the 1962 German Hillclimb Championship in a Ferrari 250GT SWB Berlinetta, which earned him an invitation from Enzo Ferrari to Maranello.

Following further successes in a Lola T70, Fiat Abarth, Borgward Isabella and Ford GT40, he drove a BMW 320i Turbo or M1 Procar well into the 1980s and, together with his son Walter, won the Touring Car Trophy in a Porsche 935 K3. Finally, he competed in the Interserie in a Porsche 962. In the meantime, he had sold his publishing house and founded Koenig Specials in 1974. The catalyst for this was the purchase of the first Ferrari 365 GT4 BBs registered in Germany, with whose performance – compared to his racing cars – he was dissatisfied.

He became so well-known that he was approached at Ferrari events and asked to carry out similar tuning work, which was initially limited to tasks such as fitting factory parts or rear spoilers copied from other racing cars, wide wheels, three-disc clutches and high-performance exhaust systems. Driven by economic growth, Koenig Specials became one of the first tuning firms to specialise in the conversion of production cars, in a sense taking over the tradition of the coachbuilders of earlier generations. Enzo Ferrari eventually forced Willy König through the courts to stop using the distinctive Ferrari ‘Prancing Horse’ emblem.

Also meaning that the Mercedes star was also no longer permitted to adorn the modified W126 and was replaced by ‘KS’ of the same size. One of the first 560 SEC conversions was commissioned by Sylvester Stallone. Various body kits were available, and the V8 – which was by no means underpowered for its time – saw its output increase from 268 to 400 PS thanks to an Albrex supercharger. Extreme width, huge spoilers and technically sophisticated twin-turbo engine variants became the brand’s hallmark and still attract enthusiasts today.

The magazine ‘Sports Car International’, published in California until 2008, suggested that Koenig Specials had sparked the trend for wide-body conversions in the 1980s, whilst the international motoring press also regarded the company as one of Germany’s leading tuners. Today, not least because tuning firms have been superseded by manufacturers’ in-house tuning divisions and customisation programmes such as BMW M and Mercedes-AMG, the company’s significance has diminished. It continues to exist, but no longer produces its own vehicles; instead, it manufactures only components, such as those used in the vehicle described here, which were produced in July 2025.

The conversion

The engine and chassis remained unchanged. Only the bodywork was modified to incorporate the Koenig components. To achieve this, the original wheel arches had to be cut out and rebuilt to create sufficient space for the Pirelli Cinturato P7 345/35 VR15 tyres on three-piece BBS rims. The bodywork was prepared for the bonding of the body panels from the Koenig kit. Initial fitting was carried out using removable rivets, with the aim of achieving uniform and symmetrical gap dimensions. The components were bolted together whilst the adhesive was setting; the bolts were later removed and openings and joints were filled seamlessly.

The paintwork

This work took around 200 hours. An identical amount of time was required for the subsequent paintwork, as the car underwent four rounds of baking to ensure an even and durable finish. The paintwork also had to ensure that no cracks would form in the stress structure of the different materials – the metal of the original bodywork and the GRP of the tuning components – during everyday use.

Authenticity

No authenticity certificate was sought prior to the car’s return. The question arises as to whether the retrofitted car can now be considered a ‘Koenig Spezial’. The company’s original cars were delivered with certificates of authenticity. The latter appear to be circulating on the market as forged versions, as do conversion kits that are not manufactured and supplied by Koenig itself. Consequently, the Benz retained the star in its radiator grille. Another point is that the German term ‘Oldtimer’ is not in common use in the USA. Here, terms such as ‘Classic Cars’ (over 20 years old), ‘Antique Cars’ (over 45 years old) and ‘Vintage Cars’ (built between 1919 and 1930) are used.

Although the term ‘Antique’ on US number plates is comparable to the German ‘H-Kennzeichen’, the difference is that the classification of historic collector’s items in the US is subject to specific requirements and comes with certain privileges. Such a licence plate is only issued to a car that – depending on the state – is at least 20 to 45 years old. This meant that the original 500SEC could be registered in this way, although the registration is not valid for everyday use, but only for journeys to historic events and test drives.

The criteria set by the ‘Classic Car Club of America’ are even stricter: only cars from the years 1915 to 1948 are considered classics, and the club only includes vehicles that ‘are distinguished by their elegant design, high technical standards and first-class workmanship’. As regards the current situation, it can be said that the classic 500SEC has not become a ‘Koenig Spezial’, but it certainly carries the reputation and quality of the workshop from the small Upper Bavarian village of Valley out into the world as a ‘Cars & Pipes Special’. The author would like to thank Cars & Pipes, Martinshof 12, 83626 Valley, for the information and photographs.