Mercedes-Benz M100 engine

The Mercedes-Benz M100 engine was a 6,333 cc (386.5 cu in)^[1] single overhead cam V8 produced by Mercedes-Benz between 1963 and 1981. The successor to the M189 version of the company's venerated 2,996 cc (182.8 cu in) straight-6 M186, it was introduced in the flagship Mercedes-Benz 600 in 1963. From 1968 to 1972, it was fitted also into the S-class body for a special high-performance Mercedes-Benz 300SEL 6.3 sports sedan that was in 1975 updated to a Mercedes-Benz 450SEL 6.9.

Mercedes-Benz M100 engine
In a Mercedes-Benz 300 SEL 6.3
Overview
Manufacturer	Daimler-Benz
Production	1963-1981
Layout
Configuration	Naturally aspirated V8
Displacement	6.3 L; 386.5 cu in (6,333 cc) (1963-1981) 6.8 L; 417.0 cu in (6,834 cc) (1975-1981)
Cylinder bore	103 mm (4.055 in) (1963-1981) 107 mm (4.213 in) (1975-1981)
Piston stroke	95 mm (3.740 in)
Cylinder block material	Cast iron
Cylinder head material	Aluminum
Valvetrain	SOHC
Compression ratio	9.0:1 (1963-1981) 8.8:1 (1975-1981)
Combustion
Fuel system	Mechanical fuel injection
Management	Daimler-Benz designed (1963-1972) Bosch K-Jetronic (1973-1981)
Fuel type	Gasoline
Oil system	Dry sump
Cooling system	Water-cooled
Output
Power output	250 PS (180 kW; 250 hp) at 4000 rpm (1963-1981) 286 PS (210 kW; 282 hp) at 4250 rpm (1975-1981)
Torque output	51 kp⋅m (500 N⋅m; 370 lb⋅ft) at 2800 rpm (1963-1981) 56 kp⋅m (550 N⋅m; 410 lb⋅ft) at 3000 rpm (1975-1981)

The original displacement of 6,333 cc (386.5 cu in) exceeded that of the first Rolls-Royce V8 engine with 6,231 cc (380.2 cu in) by approximately 0.1 L. In the 1970s, AMG enlarged M100 engines to 6,8 litre, for racing and road use. In the US, catalytic converters and unleaded fuel caused loss of power. Rolls-Royce had now 6,750 cc (411.9 cu in) (6.8 L), and for the Mercedes-Benz 450SEL 6.9 (1975-1981) the M100 engine was enlarged to 6,834 cc (417.0 cu in) which are close to 6.8 L, but as German tax laws required that a 101 cc engine would be taxed like a 200 cc engine, it was accordingly badged as 6,9.

The M100 featured a cast iron block, aluminum alloy heads, and aircraft-style sodium-filled valves operating against hardened valve seats. As in all Mercedes-Benz automobile engines, the crankshaft, connecting rods and pistons were forged instead of cast.

Each hand-built unit was bench-tested for 265 minutes, 40 of which were under full load. When introduced, it utilized a complicated 8-piston mechanical fuel injection system designed and built in-house by Daimler-Benz. The 6,834 cc (417.0 cu in) version used a simpler Bosch K-Jetronic Continuous Injection System.

The 6.3 L engine was conservatively rated at 250 PS (184 kW; 247 hp), with 51 kp⋅m (500 N⋅m; 369 lb⋅ft) of torque helping to compensate for the 2.85 to 1^[2] final drive ratio necessary for sustained high-speed cruising.

In non-US trim, the larger engine produced 286 PS (210 kW; 282 hp) with 550 N⋅m (406 lb⋅ft) of torque. The North American version, introduced in 1977, was significantly less powerful at 250 PS (184 kW; 247 hp) and 488 N⋅m (360 lb⋅ft) of torque due to more stringent emissions control requirements.

The "6.9"-liter M100 used a "dry sump" engine lubrication system, which both enhanced longevity and reduced overall engine height. Originally developed for racing as a way to prevent engine oil foaming at high crankshaft speeds, which in turn would create a serious drop in oil pressure, it allowed sustained high speeds at full engine power. The M100 system circulated a massive twelve litres of oil through the engine and a storage tank mounted inside the right front fender, as opposed to the usual four or five litres found in V8s with a standard oil pan and oil pump configuration. The dry sump system also had the benefit of extending the oil change interval to 12,500 mi (20,100 km). This, along with hydraulic valve lifters which required no adjusting and special cylinder head gaskets which eliminated the need for periodic retorquing of the head bolts, made the 6.9 nearly maintenance-free for its first 50,000 mi (80,000 km).