Real strange, since there is a 2.5-liter six-cylinder with overhead camshaft since 1928 and the receives a successor with 2 liters of displacement and upright valves, so basically three steps back. Is presumably due to the economic crisis with the 'Black Friday 1929 and this unit much cheaper to produce. But the OHC engine does not disappear completely but rather is assigned to the model 'Isis'. Both disappear in 1935. 07/13