OM326

Introduced in 1956 as the largest six Daimler-Benz had yet built for its heavy trucks, the OM 326 abandoned the single common cylinder head. Each cylinder got its own, carrying four overhead valves, which forced the bores further apart and made both the engine and the bonnet ahead of it noticeably longer. It was still a pre-chamber design — glow plugs, 20.5:1 compression, a cast-iron block of some 805 kg — and in its strongest tune gave 200 PS at 2,200 rpm for the LP 326 cab-over and, later, the L 337, L 338 and L 1620.

Then Christoph Seebohm's 1956 weight laws capped two-axle trucks at 12 tonnes while allowing three axles 16, and Stuttgart answered with the LP 333 — the twin-steering-front-axle "Tausendfüßler", whose OM 326 sat inside the cab beside the driver, radiating heat and noise and awkward to reach even for topping up the oil. 1,833 were built before the rules relaxed in 1960 and the whole exercise lost its point. A horizontal OM 326h went under the floor of the O 317 bus. In 1964 the pre-chamber went too: the same 128 × 140 mm dimensions returned as the direct-injection OM 346.