After gaining the role of a big company, it has been thought that Maserati would have left the small deployments, even if such policy had proven to be rewarding in the past. The massive presence, in Europe, of American soldiers had been a wonderful promotional vehicle for the British and German houses, devoted to build sports car with low and medium deployment. When they went back home, the USA discovered the brilliant European cars, much more exciting than their huge vehicles. The liveliness of the sector represented an important spur also for Maserati, which had already received a lot of success in America, with the two victories at Indianapolis, with the 8CTF. But entering that huge market, signified to reach production rhythms very utopian for the company.

In spite of perplexities, the program started, but had been developed only on its agonistic side, which, in the intentions, had to give just an advertising support. The program was based on a 1500 cc. car, which, abandoned the hypothesis of a GT car, brought to life the 150S type, protagonist of epical fights with Porsche, EMW, and their "cousins" OSCA, built by Maserati brothers. The project started in 1953, under the direction of Mr. Bellentani, with the development of the engine. Even if the engine of the 4CF2 had been taken as a starting point, an integration between constructive simplicity and advanced technology (concepts that were gaining more and more importance) had been researched. The design of the engine anticipated 4 cylinders in line, with under-square dimensions. That choice had repercussions on the distribution, with two shafts whose valves had an opening angle of 80° and were driven by roller balances. The high rotation rates brought some hesitations regarding the use of screw springs, so that needle springs had been preferred, similarly for the recall of the balances. Utilizing a particular device, the valves, rotating around their axle, progressively settled. Because of the wide surface of the piston, the use of a double starter, with Marelli coil ignitions situated in front of the engine, and of an alimentation with two double-bodied Weber carburetors had been expected.

To see the 150S on the racing truck a lot of time had to pass; the delay had been caused by the pressing duties which involved the six-cylinders. Consequently, at least to start the tests of the engine, the motorboating proved to be a good test-bed. During October 1954, the first engine had been installed on the "Maria Luisa IV" hull, brought by Liborio Guidotto to win the world championship title. That engine, on a par with the second exemplar, prepared for the following year, differed from the production standard because of its working with an alcoholic mixture. That’s the reason why it had a much higher compression ratio, 11,5:1, and starter with two magnets. Maintaining this solution also on some engines for the cars, the compression ratio had been a lot lower, due to the use of commercial fuel. During the dead times which anticipated the 1955 racing season, finally started the production of the car, with a suffered project. It can be shown by the three ways in which the problem had been faced: the first foresaw a reticular chassis for the hypothetical tourist version, almost immediately abandoned. The other two were based on the compared analysis of two well-known solutions of the A6GCS and on those which had to be the new concepts of the car: a chassis with classical solutions, but not less functional, suggested by the experience gained in other sectors. In both cases the starting point was a series of pipes with a mixed circular and ovoid section, but the first also had the unbending rear axle and the front of the A6GCS, while the second had a Dion axle and newly designed front suspensions, but with the typical Maserati style. Moreover, the first mounted the 2 liters and 4 cylinders engine of the 200S. Notwithstanding the functionality of the hybrid based on components of the A6GCS, Mr. Alfieri, chief of the development, preferred to favor the concepts expressed by the authentic 150S.

During April 1955, under the guide of Guerino Bertocchi, took place a large number of tests, in which at least a dozen of potential clients participated. The most of the data gathered, had been helpful to define the car under each particular aspect, progressively correcting the vices of youth. Notwithstanding this, it can be said that the 150S didn’t meet completely the canons of a commercial car. Its maneuverability and behavior needed a careful and expert drive, not always noticeable in the less prepared buyer. The production started in 1955, with the delivery of the n°1654, while the n° 1652, first exemplar ever built, remained temporarily in the plant. The n°1653 was instead rethought, with the lengthening of the distance between the wheels, of 100 mm, solution adopted on all the exemplars from the n°1656, together with other relevant changes. These regarded the sleigh anchorage of the DeDion axle, with the suppression of the primitive reaction triangle and with the higher consistency given the transversal leaf spring, normally mounted in a lower position. The pipe connecting the wheels, was set on the back of the differential box, and all the design of the rear axle was of an exemplar linearity, allowed by placing the gear in a block with the engine. Also this peace was totally new, with 4 synchronized Porsche speeds and excellent maneuverability.

Developing the model, in 1956 a 5 speed gear had been used, often together with a ZF self-blocking differential. In the same way, it hadn’t been rare the use of starter with two magnets and of a supplementary tank for the fuel, placed on the side of the driving seat. The principal one, normally containing a 100 liters, was placed in the rear bonnet, near the lubricant tank, of a 16 kg capacity. All the 1955 bodies, made by Celestino Fiandri, were inspired by the lines of the 300S. Due to the smaller dimension, the result was more massive and roundish, with a wide air scope, often choked with a proper shield. The driving seat was on the right, with a wide dashboard which cover a bit of the sight. A small windscreen offered a limited protection to the driver’s face and the passenger seat was, normally, hidden under an aluminum panel, perfectly connected with the rest of the body. These choices had been strengthened with the unexpected demonstration of power given by Behra at the Nürburgring 500 km, on August 28, 1955. Conventionally the debut of the 150S goes back to this date, but it seems hazardous to exclude any possible preceding presence, in some minor race, of the four cars which were already in the possess of the respective owners. However, the clamorous affirmation of Behra’s n°1656, against thirteen Porsche and four fast 6 cylinders EMW, brought interest, curiosity and lots of bookings on the 150S. But Maserati gave proof of realism, preparing those variants necessary to maintain its hegemony. From the Nürburgring experience, Mr. Bertocchi suggested the opportunity of small and large changes.

The more relevant ones were based on the comparison of the weighs of the racing cars, on their aerodynamic efficiency and on the need of a 5 speed gear. It also suggested a different supplementary tank, the predisposition of the lifting trolleys of the vehicle, a rational arrangement of the tools and of the spare tyre, as well as making a closet for food and thermos for drinks. Maliciously he also suggested to provide and avoid the manumission of the revolution counter by the driver, because Behra arrived at the end of the tests with the red needle still at 7200 rpm, but with springs and valves out of order, which let suppose that at least a 2000 rpm higher regime had been reached. Fundamental points of the development were, however, weigh and aerodynamics. Regarding the first, Mr. Alfieri turned his attention to the efficiency of the body: the result of this research found expression in the exemplars built in the 1956 season, starting from n° 1660, brought by De Tomaso/Tomasi to the fourth absolute position and the first of its class, at the 1000 km of Buenos Aires. The rounding line of the first type had been substituted by a more angular design, with tight and perpendicular sides, the apparently high and nearly cut off tail, the low and long frontal, with flat bottom. Their production, with the exception of the exemplars n° 1665, 1666, 1667, had been made by Fantuzzi.

Following that direction, the stylistic and formal evolution went on unending, to reach more racy and functional shapes, seen at the Supercortemaggiore Trophy and more assiduously developed on the 2 liters one. The need to provide a various and numerically important production, put aside the role of the 150S, whose construction of chassis had been given to Gilco. That’s the reason why, notwithstanding some good proofs, as Amelio Garavaglia’s success at Messina 5 hours, against Hermann’s official Porsche, and the Bourilliot/Perroud wonderful race at Le Mans, the development of the 150S had been definitively abandoned at the end of 1956. The series production took a different direction, at the end of 1957, a spider, based on the engine of the 150S and using different components, had been made. In fact, the base was a 200S modified chassis, rear axle from the A6GCS, clutch, gear box, steering and hubs from the A6G54, and so on. The engine had been correctly adapted for the street use, with a drastic reduction of the compression ratio, lubrication with only one deliver pump, and sheet iron sump, with a 6 kg capacity. The body had been made by Fantuzzi, who, even being well-known for his ability in the construction of race cars, didn’t have much experience in the granturismo sector. However, he took the best of what he’d seen being done by Allemanno, Frua, Zagato on the A6G54. For the problems of the period, the car didn’t have the right success, neither a buyer, and ended its days on the corner of the plant. During the 60s, the 4 cylinders engine of 1500 cc, made a comeback, because of the clients, who wanted to have it mounted on English chassis, to race at the Formula2 Championship.

From the following season, the small cars had been promoted to the grand prix role, and in that way, there had been a kind of return to the Formula 1. The starting idea of the engine was the one of the 150S, but the had had been redesigned following the experience made with the type 60. Because of bulk reasons, the power takeoff for the double-starting distribution, had been shifted to the end of the aspiration camshaft. With the usual Weber 45DCO3 carburetors, but with a different compression ratio, brought to 10,5:1, the power reached the level of 165 hp @ 8500 rpm. Thanks to the use of some light magnesium alloy components, the total weigh was of 130 kg. Due to its substantial restructuring, the engine adopted the new denomination "Type 6", and had been sold at 2.5 million liras, The first buyer had been the Centro-Sud team, which inscribed a Cooper-Maserati at the 1960 Pau GP for Master Gregory. Afterwards, these hybrids incredibly proliferated, buy the more used chassis had been, a part for the Copper’s, the Lotus’s, while the Emeryson, made by E.N.B. (Equipe Nationale Belgique) revealed to be disastrous.

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