The 4CLT grew out of experiments Maserati conducted with the older 4CL from 1947 onward. The 4CL — first raced in 1939 — used a conventional twin box-section spar chassis and a 1,490.85 cc inline-four engine with a single supercharger producing around 220 bhp. As Alfa Romeo raised the stakes with two-stage supercharging on its 158, Maserati responded by testing tubular chassis members on modified 4CL cars to improve torsional rigidity, which was needed to handle the additional torque from a revised, more powerful engine.
The result was the 4CLT — the T denoting its tubular chassis. The revised inline-four engine featured roller bearings for the crankshaft, forged rear suspension components, and twin superchargers lifting output to approximately 260 bhp. The car ran hydraulic dampers as standard from the outset.
The first 4CLT variant took its unofficial name from its debut race: the 1948 San Remo Grand Prix, where Alberto Ascari drove a works car to victory on its first competitive appearance. Luigi Villoresi and Reg Parnell won five more races for Maserati in 1948, establishing the 4CLT as the leading privately obtainable Grand Prix car of the era.
In 1949, minor modifications — revised brake drum cooling and cockpit layout changes — produced what some referred to as the 4CLT/49, though the factory never used that designation. Juan Manuel Fangio and Toulo de Graffenried joined the 4CLT's roster of frontrunners, and Maserati drivers won nine of the first fifteen races of the 1949 season. De Graffenried's win in the British Grand Prix was among the highlights. However, increasingly competitive Ferrari and Talbot cars closed the gap in the second half of the year, limiting Maserati to three further wins.
The 1950 season brought the inaugural FIA World Championship of Drivers. Maserati again upgraded the 4CLT's engine with a multi-part crankshaft, lightened and balanced connecting rods, stronger superchargers, and revised ignition timing, pushing output to a claimed 280 bhp while shedding 10 kg from the car's weight. Despite approaching Alfa Romeo 158 levels of performance in short runs, the upgrades proved too demanding for the engine's ageing fundamental design, and reliability suffered. The season's only Formula One victories came in non-championship events: Fangio won the Pau Grand Prix on the same day Parnell took the Richmond Trophy at Goodwood, and David Hampshire won the Nottingham Trophy later in the year.
In the World Championship itself, the 4CLT's best result came courtesy of Louis Chiron, who finished third in the 1950 Monaco Grand Prix driving a Sanremo-specification car. From 1951 onward the 4CLT was progressively outpaced, as newer, lighter machinery emerged from European factories.
The 4CLT/50 designation was applied to a small number of Sanremo cars modified for the 1949–50 Temporada Formula Libre series in Buenos Aires, where the engine was bored out to 1,719 cc to take advantage of the open capacity rules. Despite these changes, Ferrari dominated the Temporada races, and the cars were reconverted to Formula One specification after the series concluded.
Enrico Platé, a long-standing campaigner of Maserati machinery, converted a 4CLT/48 into a Formula Two variant by removing the superchargers, raising compression, and enlarging capacity to the F2 class limit of 2.0 litres. The Maserati-Platé 4CLT also had its wheelbase shortened to reduce weight and sharpen handling to suit the lower-powered engine.
Prince Bira modified his 1949-specification 4CLT to accept a 4,450 cc OSCA V12 naturally aspirated engine producing around 300 bhp. Bira won a Goodwood race with the hybrid early in 1951, but in its only World Championship appearance, at the 1951 Spanish Grand Prix, the car retired on the first lap.
De Graffenried won the Richmond Trophy and Giuseppe Farina won the Paris Grand Prix in 4CLTs in 1951, but the switch to Formula Two regulations for the World Championship from 1952 left the old cars overweight and underpowered compared to a new generation of smaller, lighter single-seaters. The 4CL and 4CLT family had been the backbone of top-level European Grand Prix racing from the late 1930s through the first two seasons of the World Championship — an unusually long competitive lifespan made possible by the disruption of the Second World War and the car's popularity with independent entrants. Many examples survive today, regularly appearing in historic motorsport events and museum collections.