This engine was the first designed by Cox but included some major parts (i.e. piston and cylinder) of the Spitzy.045 engine designed by Mel Anderson. It employed a twin reed valve which was later used for the Space Bug. The engine was a major engineering achievement for its time, by incorporating reduction gears, fuel tank, flywheel and muffler all into one "Power Pak." The air intake was via one of the axles.