M100

The 600 of 1964 needed an engine with no equal in Germany, and the M100 was sized to make the point: at 6,333 cc it came out roughly a tenth of a liter larger than the Rolls-Royce V8 of the day. Cast-iron block, aluminum heads, aircraft-style sodium-filled valves against hardened seats, forged crankshaft, rods and pistons, and Bosch eight-plunger mechanical injection. Every unit was assembled by hand and run on a test bed for 265 minutes, forty of them under full load, before it was passed.

It should have stayed in the 600. Instead the test engineer Erich Waxenberger fitted one to a W 109 in his own time; Rudolf Uhlenhaut heard the car circulating on the works track, drove it, and took the idea to the board. The 300 SEL 6.3 reached Geneva in 1968 and sold 6,526 — the fastest saloon in the world. When Rolls-Royce enlarged its V8 to 6,750 cc, Stuttgart answered at 6,834 cc for the 450 SEL 6.9, adding a dry sump and twelve liters of oil to clear the W 116’s lower bonnet, and named the car for the argument rather than the arithmetic.