Chrysler Corporation in the US had been working since 1966 on an inline 6-cylinder engine, called the D-engine, to replace the
Slant 6 (G-engine) in
Dodge trucks, but abandoned the effort after prototypes were built. This was Chrysler's first thin wall (lightweight) cast iron engine design.
Chrysler Australia wanted a new six-cylinder engine for use in the Australian
Chrysler Valiant, and so Chrysler USA sent a prototype engine to Chrysler Australia's engineers to continue developing the D-engine. The first 245 cu in (4.0 L) variant was released for the 1970 model year in the VG-model Valiant.