The Leyland OE engine (OE.138/OE.160) is a diesel, pushrod (OHV) straight-four engine based on the Standard 23C design and redesigned by Leyland Motors subsequent to their 1961 takeover of Standard-Triumph.
Standard had earlier updated the 23C with glow plugs in each cylinder head; this was retained for the OE.138, as was the Ricardo pre-combustion (indirect injection) design.
[1] The OE.160's bigger bore and stroke were made possible by using thinner, press-fit cylinder liners and a longer-throw crankshaft.
[1] The Low Speed engines, designed for continuous power supply, produced 36 and 40 hp (27 and 30 kW) respectively.
[2] The smaller version was also installed on the Standard Atlas (later known as the Leyland 15/20) light van.