In 1953 Vittorio Bellentani began a study of a 1.5-liter 4-cylinder that Maserati thought could be fitted in a new GT, a hypothesis that was later discarded in favor of a Sport. The project was inspired by the 4C F2 engine which in 1952 was built under the direction of Alberto Massimino. The displacement was 1484cc and the power reached 140 horsepower. The chassis, which initially was to follow that of the A6 GCS, was heavily modified, with the adoption of a De Dion bridge. The bodywork was similar to that of the 300S. The 150S achieved several successes in the Sport 1500 class between 1955 and 1958, as well as a dozen overall victories. A 1500 engine was fitted by British driver Brian Naylor to a Lotus 11 which proved to be very competitive.