Mercedes-Benz M186 engine
The Mercedes Benz M186 Engine was a 3.0–litre single overhead camshaft inline-6 developed in the early 1950s to power the company's new flagship 300 "Adenauer" four-door saloon. It made its debut at the Frankfurt Motor Show in April 1951.
Designed to give reliable service under prolonged hard use, the iron block/aluminum head engine featured deep water jackets, an innovative diagonal head-to-block joint that allowed for oversized intake and exhaust valves, reverse-flow cylinder head, thermostatically controlled oil cooling, copper-lead bearings, and a hardened crankshaft.
Variants of the M186 went on to be used in the exclusive 300 S/300 Sc gran tourer, W194 300SL racer, iconic gullwing 300SL sports car and roadster, and Mercedes top-end 112-series 300SE sedans and limousines, and coupes and cabriolets of the early to mid-1960s. Production ended in 1967, four years after the introduction of the 600 Grosser Mercedes and the M100 V-8.
The various versions of the engine produced from as compression ratios rose and the number of carburetors multiplied or were replaced with fuel-injection.
While sharing many design features with Mercedes' M180 engine introduced at the same show, the two were of completely different design with little or no inter-changeability of parts.
The term "big six" is sometimes used to distinguish the large block 3.0 L M186 from the small block M180 and its derivatives.
M186 Variants
M186
The 3.0–litre M186 was introduced in 1951 for use in the company's flagship 300 "Adenauer" four-door saloon. It had a slightly under-square bore and stroke of, featured an overhead cam, and an aluminum head with an innovative 30-degree diagonal head-to-block joint that allowed for oversized intake and exhaust valves. Designed to give reliable service under prolonged hard use, the engine featured deep water jackets, thermostatically controlled oil cooling, copper-lead bearings, and a hardened crankshaft.Fitted with twin downdraft Solex carburetors it produced at a 6.4:1 compression ratio.
M188
The M188 was introduced in 1952, adding a third downdraft Solex carburetor to the M186; with an increased 7.8:1 compression ratio it produced at 5000 rpm, up substantially from the M186's then. It was only available in the W188 300 S coupé/cabriolet/roadster, through 1955.M189
The M189 was released in August 1957 for use in the 300d pillarless limousine, replacing the still underpowered W186 300c's M186 engine's twin Solex carburetors with a Bosch mechanical multi-point fuel injection system. The change substantially upped performance to at 5500 rpm.The engine then appeared in 1961 in the W112 300SE series of sedan, coupe, and cabriolet, as well as its long wheelbase derivative two years later. From 1964, power output was. The final incarnation of the M189 was in the W108 300SEb and W109 300SEL of 1965–1967.
M194
The M194 engine was developed in 1952 for the W194 300SL racer. Only 10 were made, the first three producing around, while the remaining seven put out around.Like the W188 used in the ultra-exclusive 300 S coupé/cabriolet, the M194 was outfitted with three two-barrel Solex carburetors. Similar to the M198 used in the production 300SL, the engine is titled 50 degrees to the left in order to reduce the height of the hood, and uses a dry sump lubrication system instead of an oil pan and reservoir. It is also mounted behind the front axle for better weight distribution.
M198
The high-performance, fuel-injected M198 was created in 1954 for the first generation of the 300 SL, known colloquially as the "Gullwing". To fit under its low profile hood the engine was tilted 50-degrees to the left. The result for the car was aerodynamic efficiency, and an enormous sand-cast aluminum intake manifold that stretched across the engine's entire breadth. In order to deliver track-ready performance, race-derived features were built in, including a dry sump lubrication system and Bosch mechanical direct fuel-injection, one of the first production cars with fuel injection.This engine originally produced DIN net at 5,800 rpm and DIN net of torque at 4,600 rpm and net at 6,100 RPM and net torque at 4,800 RPM. An optional high-performance "Sport" camshaft became available, which was the only configuration offered for the Roadster version of the 300 SL when it made its debut in 1957. Production ended in 1964.