The 450 SEL 6.9 was unveiled at the 1974 Geneva Show. It combined much of the hardware of the W116 S-Class that arrived in 1972, the first large Mercedes sedan to carry that storied designation, with an upgraded version of the 6.3-liter M100 single-overhead-cam V-8 originally developed to power Benz\u2019s 1963 Rolls-Royce fighter, the 600<\/a>, and subsequently slotted under the hood of the W109 SEL sedan to create the 300 SEL 6.3.<\/p>\n\n\n\n For the 450 SEL 6.9, the engine was bored to increase its capacity to just under 6.9 liters and fitted with Bosch K-Jetronic fuel injection and a 3.2-gallon dry-sump lubrication system. Like the original M100, the 6.9-liter version had a forged crankshaft and forged connecting rods and pistons. The valves were sodium filled to keep them cool at high speed. Each engine was hand-built and bench-tested for more than four hours, 40 minutes of which was under full load.<\/p>\n\n\n\n In European trim, the 6.9-liter M100 developed 282 hp at 4,250 rpm and 406 lb-ft at 3,600 rpm. In the U.S. version of the car, which was introduced in 1977 as the Mercedes-Benz 6.9, emissions control regulations cut power to 250 hp and torque to 360 lb-ft. For context, most contemporary American V-8s of similar capacity were by then struggling to make 200 hp, though Ford and Chrysler offered special police pursuit big-blocks that in 1977 produced 197 hp and 255 hp, respectively.<\/p>\n\n\n