OM346

Daimler-Benz had been injecting diesel into a pre-chamber since 1923. In 1964 it stopped. Two direct-injection sixes arrived together — the small OM 352 and, replacing the OM 326, the 10.8-liter OM 346, which kept its predecessor's 128 × 140 mm dimensions and its unusual four-valve heads but burnt the fuel in a bowl in the piston crown instead. The gain was in consumption as much as output: 180 PS in the mild tune, 202 PS in the strong one, and 210 PS if the buyer specified the thermostatic viscous fan that only took power when the coolant asked for it.

It went into the L 1418 and the LP 1418 and LP 1620 cab-overs, which had appeared only a year earlier, and lay on its side as the OM 346h beneath the floor of the O 317 bus. Its own career was short in name only: in 1967 Daimler-Benz lengthened the stroke from 140 to 150 mm, took the six to 11.6 liters and called the result the OM 355. Some owners of the old pre-chamber trucks made the change themselves — at least one surviving LP 333 runs today on an OM 346 fitted in place of its original OM 326.