The Nissan H series of automobile engines is an evolution of the Nissan "R" engine which was based on the 1.5-liter, three-main bearing "G" engine used in the 1960s. Both inline-four and inline-six versions were produced. It is a pushrod OHV design with iron block, early models with an iron head, later models with aluminum head. Versions of this motor have been used in many Nissan autos and forklifts, well into the eighties and a version called H20II is still in production today. The SD diesels are based on this series of motors (bore spacing and basic block layout)