The Holden Grey motor is often referred to as the Holden side plate. The engine earned its name as they were painted grey from the factory. They came in 2 sizes, 138ci and 132ci.
More engineering and after market modifications have gone into this engine than any other engine in Australian automotive history.
Guy check out this vid of the grey. From 60HP standard more then doubling with a small cam and carbies. Imagin back in the day having twice the HP of the standard car this think would rocket back in the day.