Mercedes-Benz M186 engine

Mercedes-Benz M186 engine
M198 variant
Overview
Production	1951–1967
Layout
Configuration	inline-6
Displacement	3.0 L; 182.8 cu in (2,996 cc)
Cylinder bore	85 mm (3.35 in)
Piston stroke	88 mm (3.46 in)
Cylinder head material	Aluminum
Valvetrain	SOHC 2 valves x cyl.
RPM range
Max. engine speed	6000[1]
Combustion
Fuel system	3 downdraft Solex carburetors Bosch Fuel injection
Fuel type	Gasoline
Cooling system	Water-cooled
Output
Power output	115–240 bhp (86–179 kW)
Torque output	294 N⋅m (217 lb⋅ft) (M198 300 SL)

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" (W186) 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 Mercedes top-end 300-series sedans and limousines, and coupes of the early to mid-1960s. Production ended in 1967, four years after the introduction of the 600 Grosser Mercedes and the 6.3 L (386.4 cu in) M100 V-8.

The various versions of the engine (M186 – M199) produced from 115–240 bhp (86–179 kW) as compression ratios rose and the number of carburetors multiplied or were replaced with fuel-injection.^[2]

While sharing many design features with Mercedes' 2.2 L (134 cu in) M180 engine introduced at the same show (such as staggered valve arrangement and rockers running off a single overhead camshaft driven by a duplex cam-chain), the two were of completely different design with little or no inter-changeability of parts.^[3]

The term "big six" is sometimes used to distinguish the large block 3.0 L M186 from the small block M180 and its derivatives.