Announced in July 1922, the OD Type 23/60 replaced Vauxhall’s 25 hp D-Type that had helped see the company through the First World War. Although the 23/60 was not as powerful as the 30-98, which was developed at around the same time by recently appointed Chief Engineer Charles Evelyn King, it shared many of its parts.

King modified the D-Type’s engine by adding a pushrod overhead valve to improve efficiency and equipped it with a Lanchester harmonic balancer that cancelled out the vibration caused by the unbalanced secondary forces that came with a four-cylinder engine. He also added a detachable cylinder head for easy access to maintain the engine which still needed to be decarbonised frequently.