M114

The W114 arrived in 1968 needing a six for its upper models, and the M114.920 was very nearly the existing M108: the same 2,496 cc from 82 × 78.8 mm, the same seven-bearing crankshaft, gray-iron block, aluminum head, single overhead camshaft and pair of Zenith carburetors. What changed was the valve timing, reworked to move torque down the rev range where a large saloon actually uses it. In that form it gave 130 PS at 5,400 rpm and served the 250 and the 250 C.

The interesting one is the M114.980. Mercedes-Benz had been building mechanically injected engines since the 1950s, but this was the first to be governed electronically: Bosch D-Jetronic, sensing manifold pressure and computing injection duration rather than metering fuel off a cam. Compression rose to 9.5:1 and output to 150 PS at 5,500 rpm, and it was fitted to exactly one model, the 250 CE. Neither version lasted. In 1972 the twin-cam M110 replaced them both, four years after the first had appeared.