Numbers first, because with the A.L.F.A. 40/60 GP they are the story: 4490 cc straight four Twin Overhead cam, 88-102 hp @ 2,750-3,000 rpm. Alfa Romeo built from 1914 to 1921, as the assembly line was turning motoring into an industry. Giuseppe Merosi drew it.
Where it came from
ALFA 40/60 GP or GP (Grand Prix) was a fully working early racing car prototype made by the company now called Alfa Romeo. Only one example was built in 1914, which was later modified in 1921. This was the creation of Giuseppe Merosi and was the first Alfa Romeo DOHC engine. It had four valves per cylinder, 90 degree valve angle and twin spark ignition. Usually Alfa Romeo DOHC engines are thought to be Vittorio Jano's creations but the first one was Merosi's GP car. This kind of engine architecture was very new for the time, originating from 1912/1913 Peugeot designed by Swiss engineer Ernest Henry.
The history of this engine architecture is unclear, but other cars with dual overhead camshafts were made by Sunbeam, Delage and Humber. This 1914 GP car was intended to take part in the French Grand Prix of that year, but for reasons unknown this never happened. In 1921 Giuseppe Campari took part in the Gentlemen G.P. in Brescia with the modified GP car, but was forced to retire due to a leaking radiator. The GP engine had a displacement of 4.5 litres (4490 cc) and produced 88 bhp (66 kW) at 2950 rpm and after modifications in 1921 102 bhp (76 kW) at 3000 rpm. The top speed of this car was 88–93 mph (142–150 km/h). It was not until the 1920s when these DOHC engines came to Alfa road cars like the Alfa Romeo 6C.
Under the skin
Power comes from 4490 cc straight four Twin Overhead cam; 88-102 hp @ 2,750-3,000 rpm is the published figure. It weighs 870 kg. Work it out per tonne and you get about 101 horsepower — brisk everyday performance. It shifts through a 4-speed Chain drive Manual. The layout matters: a front engine drives the rear wheels, the classic proportion — long bonnet, cabin set back — that most people picture when they picture a sports saloon or a grand tourer. The wheelbase is 2950 mm. These are manufacturer figures carried by Wikipedia and Wikidata, not road-test measurements.
In context
Its family tree is legible: its successor was the ALFA 40/60 HP; assembly was at Milan, Italy. Its contemporaries in the catalogue — the Vauxhall D-Type, the Bugatti Type 18 — show what else the money bought that year. Nearby in the Alfa Romeo catalogue sit the A.L.F.A 12 HP and the A.L.F.A 15 HP.
What it costs now
MotorJury scores cars on the United States complaint and recall record, and the A.L.F.A. 40/60 GP has none: too old, too rare, or never sold there. Its value today is a collector's question, decided by provenance and condition rather than by a class average.