Subaru EG engine

Subaru uses a four or five character code to identify all of their engines.

The EK series is a straight twin two-stroke cycle with early air-cooled versions later replaced with water-cooled configurations in 1971. The engine was upgraded to a four-stroke SOHC in 1973 to meet Japanese Government emission regulations.

The (Japanese: ) was used from 1958 until 1989 in most Kei car models.

Air Cooled two-stroke

Used in the Subaru 360 (1958–1968) and Sambar (1961–1970).

Used in the Subaru 450 (MAIA) Japan & North America (1960–66)

Used in the Subaru R-2 1969–1971 and Subaru Sambar 1970–1973

Water Cooled Two-stroke cycle

Used in the Subaru R-2 1971.10-1972.07, Subaru Rex 1972.07-1973.10, Subaru Sambar 1973.02-1976.02

Water Cooled four-stroke SOHC with SEEC emissions system (later SEEC-T), alloy block and head.

Used in the Subaru Rex K22 from 1973.10–1976.05, Subaru Sambar February 1976-May 1976

Used in the Subaru Rex 1976.05–1977.05, Subaru Sambar 5 from May 1976 until March 1977

...
Wikipedia