All models feature the four cylinder, all-light-alloy Alfa Romeo Twin Cam engine in various cubic capacities from 1290 cc to 1962 cc, all with two valves per cylinder. All versions of this engine fitted to the 105 series coupés featured twin carburettors, except for US market 1750 GTV and 2000 GTV cars which were fitted with fuel injection. Competition models featured cylinder heads with twin spark plugs.