Alfa Romeo produced possibly the first European straight-six engine for the 1921-1923 Alfa Romeo G1 luxury car, which was powered by a 6.3 litre flathead engine. Alfa's straight-six engines evolved into the overhead valve design used by the 1922-1927 Alfa Romeo RL and the overhead camshaft engines used in various Alfa Romeo 6C road cars and racing cars 1927-1954. The last Alfa Romeo model using a straight-six was the 1961-1969 Alfa Romeo 2600 (1961–1969), before the company switched to V6 engines due to their shorter length and the torsional problems experienced in the long crankshafts of the Alfa straight-six engines.