The mega-elusive McCulloch series of model engines are not to be confused with the far better-known McCulloch chainsaw engines from America! The model engine series represented one of a number of attempts by small-scale Australian manufacturers during the early post-WW2 period to provide Australian modellers with home-grown model engines. At the time, import and currency restrictions resulted in engines fom outside Australia being in very short supply. This opened the door for small Australian grass-roots manufacturers to have a go.
The maker of the McCulloch engines was Alan E. "Billy" McCulloch of Adelaide, South Australia (my own birthplace!), who had qualified after the war as a fitter and turner and then acquired his own new Qualos centre lathe in 1947 (the year in which I was born!). While working with his father on the construction and maintenance of fairground equipment such as Ferris wheels, Alan began to construct model engines on the side.
Diesel engines were produced in both 2 cc and 5 cc displacements, the latter model being based upon Leon Shulman's Drone 5 cc diesel from America. These diesel models were followed by a 5 cc RRV glow-plug motor called the Delta 490 which was developed by Alan in collaboration with Bill Evans of the well-known distribution house of Model Aircraft Industries (MAI) of Glenelg, South Australia. Alan McCulloch's involvement with this model appears to have been essentially confined to the design and tooling stages - he evidently ended his involvement with model engines after the completion of those tasks. The actual manufacture of the Delta 490 series was carried out in a factory in North Unley which Bill Evans rented for the purpose. Production apparently continued until 1953, after which the easing of import restrictions rendered further production uneconomic.
Full details of the McCulloch engines may be found in an excellent article by Maris Dislers and the late David Owen which remains available on the late Ron Chernich's "Model Engine News" (MEN) website.