Holden straight-six motor
The Holden straight-six motor is a series of straight-six engines that were produced by General Motors Holden at their Port Melbourne plant between 1948 and 1986. The initial Grey motor was so dubbed because of the colour of the cylinder block, later motors came in the form of a Red, Blue, Black, and the four-cylinder Starfire engine.
Source: Wikipedia — Holden straight-six motor (CC BY-SA 4.0)