In the late 1930s, continued rapid development in the increasingly competitive international voiturette class, and the introduction of the Alfa Romeo 158 and ERA B- and C-type models, forced the Maserati brothers into designing a new, square-bore, inline-4-cylinder engine, with a bore and stroke of 78 mm for a total displacement of 1,490.85 cc (1.5 L).

Conventional in its architecture, twin box-section spars ran the length of the car joined, ladder-fashion, by smaller cross members, although the 4CL design did incorporate more aluminium componentry than its forebear.

Continued engine development, in response to Alfa Romeo's post-war introduction of two-stage supercharging, began to expose weaknesses in the chassis design.

Embarrassingly for the works team, following this disappointing debut the 4CL's first taste of victory came in the hands of privateer Johnnie Wakefield at the Naples Grand Prix, two races later.

Villoresi took the 4CL to victory in the 1940 Targa Florio, but with entry restricted to Axis countries, and only Maserati fielding a factory team, the opposition was hardly world class.

The improvements in torsional rigidity that the tubular construction brought were required to counteract the increases in torque and power resulting from the twin-supercharger upgrade of the elderly inline-4 engine.

Other changes included the use of roller bearings for the crankshaft, forged (rather than cast) rear suspension components, and the chassis was designed to run with hydraulic dampers from the outset.

For 1949, minor modifications to the brake drums, switching from vanes to slits for cooling, along with small changes to the cockpit control layout and a repositioned oil header-tank resulted in a car sometimes referred to as the 4CLT/49.

A multi-part crankshaft, lightened and balanced rods, a more powerful pair of superchargers and changes to the ignition timing took engine output up to a claimed 280 bhp (209 kW).

Although moderately competitive in short runs, the final upgrades proved to be too much for the decade-old powerplant's design and the 4CLT's Grand Prix performance was hindered by engine failures.

In late 1949 a number (two or three, depending on source) of the remaining Sanremo cars were converted for use in the Temporada series Formula Libre races in Buenos Aires, Argentina, in the 1949 to 1950 summer season.

De Graffenried won the Richmond Trophy, and Giuseppe Farina the Paris Grand Prix, in 1951, but with the switch to Formula Two rules for the World Championship from 1952 onwards, the old 4CLT chassis were found to be overweight and underpowered in comparison to their newer rivals.

Despite having been the mainstay of top-flight racing since the end of the 1930s, the 4CL and 4CLT rapidly fell from favour, as smaller and lighter machines began to emerge from European factories still recovering from the effects of war.