Mercedes-Benz R107 and C107

The Mercedes-Benz R107 and C107 are sports cars which were produced by Mercedes-Benz from 1971 until 1989, being the second longest single series ever produced by the automaker after the G-Class. They were sold under the SL (R107) and SLC (C107) model names in a variety of names indicating the displacement of the engines.

The R107/SL was a two-seat convertible with a detachable roof. It replaced the W113 SL-Class in 1971 and was replaced by the R129 SL-Class in 1989.

The predecessor W113 was notably successful in North America, with 19,440 units (40%) of 48,912 total units sold in the US. The R107 and C107 were even more focused on the American market, with specialized engines, bumper designs, headlights, and emissions management designs. The R107 and C107 sold 204,373 units in the US (68%) of 300,175 total units sold (excluding grey market sales into the US).

During its production run, the SL was the only roadster offered by Mercedes-Benz. The C107/SLC was a four-seat car with a fixed roof and an optional sliding steel sunroof. It replaced the W111 Coupé in 1971 and was in turn replaced by the C126 S-class coupé in 1981.

Model history
The R107 and C107 took the chassis components of the midsize 1968 Mercedes-Benz W114 model and mated them initially to the M116 and M117 V8 engines used in the W108, W109 and W111 series. The body styles for both R107 and C107 did not change materially from introduction in 1971 to their end of production in 1981 (coupé) and 1989 (soft-top) respectively.

The SL (R107) variant was a 2-seat convertible/roadster with standard soft-top, with optional winter hardtop and only rarely ordered very small rear bench-seat. The SLC (C107) derivative was a 2-door hardtop coupé, on a 36 cm longer wheelbase, and with normally sized rear seats. The SLC was the first and only time that Mercedes-Benz based their S-class coupé on a stretched SL roadster platform, rather than on a large S-class saloon. The SLC replaced the former saloon-based 280/300SE coupé in the Mercedes lineup, while there was no two-door version of the W116. The SLC model run ended in 1981, much earlier than the SL. It was replaced by the considerably larger 380SEC and 500SEC, once again derived from the 1980 S-class line.

Volume production of the first R107 car, the 350SL, started in April 1971 alongside the last of the W113 cars; the 350SLC followed in October. The early 1971 350SL are very rare and were available with an optional 4 speed fluid coupling automatic gearbox. The 1971 4sp auto were quick cars for the day with 0-60 mph in 8 seconds. In addition, the rare 1971 cars were fitted with Bosch electronic fuel injection.

European models and engines
The 350SL and 350SLC for the European market used a 3.5 liter V8 engine. From July 1974 both SL and SLC could also be ordered with a fuel-injected 2.8L straight-6 as 280SL and 280SLC.

In September 1977 the 450SLC 5.0 joined the line. This was a homologation version of the big coupé, featuring a new all-aluminium five-liter V8, aluminium alloy bonnet and boot lid, as well as a black rubber rear spoiler and a small front lip spoiler. These changes resulted in a reduction in weight of over 100kg when compared to the 'old' 450SLC. The '5.0' was built in limited numbers, only 2,769 being completed between 1977 and 1981. Maximum speed of the '5.0' was some 10km/h faster than that of the '4.5' at around 225km/h. The 450SLC 5.0 was produced in order to homologate the SLC for the 1978 World Rally Championship.

Starting in 1980, the 350SLC, 450SLC, and 450SLC 5.0 models (like the 350SL and 450SL) were discontinued in 1980 with the introduction of the 380SLC and 500SLC in March 1980. At the same time, the cars received a very mild makeover; the 3-speed automatic was replaced by a four-speed unit, returning to where the R107 started in 1971 with the optional 4 speed automatic 350SL (3.5lt).

The 280SLC, 380SLC, and 500SLC were discontinued in 1981 with the introduction of the W126 series 380SEC and 500SEC coupés. A total of 62,888 SLCs had been manufactured over a ten-year period of which just 1,636 were the 450SLC-5.0 and 1,133 were the 500SLC. Both these models are sought by collectors today. With the exception of the R171 SLK 55 AMG Black Series and the SL65 AMG Black Series, the SLC remains the only fixed roof Mercedes-Benz coupé based on a roadster rather than a saloon.

Following the discontinuation of the SLC in November 1981, the 107 series continued, initially as the 280SL, 380SL, and 500SL. At this time, the V8 engines were re-tuned for greater efficiency, lost a few horsepower and consumed less fuel, largely due to substantially higher (numerically lower) axle ratios that went from 3.27:1 to 2.47:1 for the 380SL and from 2.72:1 to 2.27:1 for the 500SL.

From September 1985 the 280SL was replaced by a new 300SL and the 380SL by a 420SL; the 500SL continued and a 560SL was introduced for certain extra-European markets, notably the USA, Australia, and Japan.

Also in 1985, the Bosch KE Jetronic was fitted. The KE Jetronic system varied from the earlier, all mechanical system by the introduction of a more modern engine management "computer", which controlled idle speed, fuel rate, and air/fuel mixture. The final car of the 18 years running 107 series was a 500SL painted Signal Red, built on 4 August 1989; it currently resides in the Mercedes-Benz museum in Stuttgart, Germany.

North American models
North America was the key market for this Personal luxury car, and two thirds of R107 and C107 production was sold there.

The R107/C107 for the North American market sported four round low-output sealed beam headlights, due to unique U.S. regulations.

Sales in North America began in 1972, and cars wore the badge 350SL, but actually had a larger 4.5L V8 with 3 speed auto (and were renamed 450SL for model year 1973); the big V8 became available on other markets with the official introduction of the 450SL/SLC on non-North American markets in March 1973. R107 and C107 cars were exported to the US with low compression 4.5 liter V8 engines to meet stringent US emissions requirements, yet still provide adequate power.

US cars sold from 1972 through 1975 used the Bosch D Jetronic fuel injection system, an early electronic engine management system. US models sold from 1976 through 1979 used the Bosch K Jetronic system, an entirely mechanical fuel injection system.

From 1974, the front and rear bumpers were dramatically lengthened, by 8 in on each end, to comply with the U.S. National Highway Traffic Safety Administration regulations that mandated no damage at an impact of 5 mph. North American market SL and SLC models retained the protruding 5 mph bumpers, even after the wisdom of the law was reconsidered in 1981.

The 450SL was produced until 1980.

The smaller engined 380SL replaced the 450SL from 1981 to 1985. The Malaise era 380SL was the least powerful of the US market R107 roadsters. Starting in 1980, US cars were equipped with lambda control, which varied the air/fuel mixture based on feedback from an oxygen sensor. The 380SL was published by Mercedes-Benz as having 0-60 mph time of 9.3 seconds for a top speed of 205 km/h. Torque for the 380SL is 232 lbft.

US gray market sales
The more powerful 500SL with a 5.0 liter engine, produced from 1980–1989, was not available in the US. This drove many customers to obtain the European specification car in the "gray market," where the vehicles were converted to meet Federal mandates, until this option was eliminated by Congress in 1988.

From 1986 to 1989, a more powerful version was available from the factory, the 560SL. It was exclusive to the USA, European, Japanese and Australian markets. Despite the larger 5.6 liter engine of the U.S. 560SL, the forbidden Euro-spec 500SL was the fastest production R107 produced (mostly because of the lack of emission reducing components).

The 500SL was published by Mercedes-Benz as having 0-60 mph times of 7.4 seconds for a top speed of 225 km/h. Torque for the 500SL is 296 lbft at 3200 rpm and for the 560SL 287 lbft at 3500 rpm.

Mechanical troubles
Model years 1975 and 1976 for the 450SL suffered from vapor lock and hard restart because of the under-bonnet position of the catalytic converter. Starting in MY 1977, the catalytic converter was moved to replace the resonator, located just behind the transmission in the exhaust system.

The 380SL/SLC engine came with a single row timing chain from 1981 through 1983. These early 380SL/SLC models were plagued with chain failure problems and the problem was corrected by Mercedes-Benz, free of charge. Some vehicles escaped the retrofit and may at some point fail as a result. MYs 1984 and 1985 came with a double row timing chain from the factory to address this issue.

Another problem area for late 450SLs was the automatic climate control system. Based on a servo which controlled coolant flow to the heater core, as well as vacuum to actuate the vents in the interior of the car, the system proved unreliable. It was installed on 450SLs through end of production in 1980. Models produced prior to 1978 had a manual climate control system, 380SL models produced from 1981 received a more reliable automatic climate control system.

South African assembly
Both the SL and SLC models were also assembled in South Africa by UCDD (United Car and Diesel Distributors) for the captive domestic market from early 1977 (on a contractor basis before Daimler-Benz A.G. acquired a majority stake of UCDD in 1984). Only about 40 units per month were built.

AMG Models
AMG offered enhancements for all R107/C107 models, while engine enhancements were not available for the 420 SL.

AMG offered two upgrade tiers for the M117. Tier 1 includes: Combustion chambers and conduits of both cylinder heads were reworked and polished, two AMG camshafts. Tier 1 rose output by 19kW (26HP). Tier 2 includes all of Tier 1 and: Larger valves and camshafts with longer valve timing and more valve stroke along with higher compression combustion chambers rising output 37kW (46HP).

In the first half of the 1980's a few copies of the 500 SL were made equipped with AMG tuned M 117 with 5.2 and 5.4 liter displacements.

AMG options included aerodynamic and appearance elements, limited slip differentials of 3.06, 3.27, and 3.46 ratios, suspension and handling equipment, AMG steering wheels, extended range fuel tanks and rare 5 speed manual transmissions.

Individual vehicles made for special clients include a 350 SLC 6.3, equipped with the M100 and the 450 SLC 6.9 equipped with M100 engine from the W116 450 SEL 6.9. AMG manufactured at least one convertible based on the 450 SLC.

450SLC 5.0
In 1978 the factory prepared two examples for the one-off Vuelta a la América del Sur, a month-long event of some 7,000 kilometres in length that took the competitors from Buenos Aires and back via Rio, Manaus, Caracas, Bogota, Lima, La Paz, Santiago and Ushuaia. The car driven by Andrew Cowan and Colin Malkin won by 20 minutes from team-mates Sobiesław Zasada and Andrzej Zembrzuski.

In 1979 a 5.0-litre 450SLC driven by Hannu Mikkola won the Bandama Rally in Côte d'Ivoire, with others finishing 2nd, 3rd and 4th. That same year the factory had used the 450SLC '5.0' to contest the Safari Rally, only narrowly missing out on victory because of suspension breakages. Nevertheless, the car driven by Hannu Mikkola finished 2nd.

Results in 1980 were worse, and the factory team was disbanded at the season's end. An Albert Pfuhl proceeded to buy all six cars, equipment, and spare parts from the works team. Pfuhl and his team built a series of cars to compete in the 1984 Paris–Dakar Rally with a white and blue "BOSS" livery. The cars finished well down the order.