If the 103's body was all-new, its engine was well-tested, having debuted in 1937 on the predecessor of the outgoing 1100 E, the 508 C Balilla 1100. Updated as type "103.000", the overhead valve four-cylinder was fed by a single Solex or Weber downdraught carburettor, and put out at 4,400 rpm—just one horsepower more than on the 1100 E. The 4-speed manual transmission had synchromesh on the top three speeds and a column-mounted shifter, fashionable at the time. The car could reach a top speed of . The new model was offered in two different versions: the spartan "Tipo A" and richer "Tipo B". The former was only available in a grey-brown paint colour, had separate front seats instead of a bench, reduced, non-chromed exterior trim, and lacked a heater and ventilation. The type B came in a choice of paint hues and interior fabrics, and could be ordered with factory-fitted whitewall tyres and radio.