Around 1910, the FS also realized that, thanks to superheater technology, compound engines could be dispensed with. Therefore the Pacifics of the class 690 II with four cylinders were commissioned. For the first time on a simple expansion locomotive in Italy, two adjacent cylinders used a common piston valve. The locomotives were designed for an axle load of 18 tonnes, but were ultimately manufactured with an axle load of only 17.1 tonnes for a better road availability.

The first nine were built with the driver's position on the right, the remaining 24 had it on the left. The firebox was partly located between the drivers and was therefore trapezoidal and narrow at the front. Since the grate had too small an area, the output was only 1,400 hp. Together with the axle load, which was still too high for most lines, no further class 690 locomotives were built. This led to a rebuild to class 691 at the end of the twenties and the class 695 to be developed as a successor.

The gruppo 691 was created by rebuilding all 33 locomotives of the gruppo 690. Although the 690 had four large cylinders, the boiler could not keep up with their steam demand at speed. So they received the boiler of the gruppo 746 that had, above all, a larger grate. They also got larger axle bearings since the original ones tended to fail at higher speeds. The cylinder size remained exactly the same.

In the result, power increased by 300 hp for a total of 1,750. This enabled 691.011 to set the Italian steam locomotive speed record to 150 km/h (93 mph) in 1939. One year earlier, 691.026 had been streamlined, but rebuilt back in 1943 since the casing did not bring great benefits. All were withdrawn in 1962 and 1963. Only 691.022 was preserved and can today be found in the museum at Milan.

The Grupo 740 of the Italian State Railway was a freight locomotive with a 2-8-0 wheel arrangement, which achieved the highest number of all steam locomotives on this railway. It was based on the Grupo 730, but unlike it had no compound engine and was superheated. From 1911 the locomotives were supplied by Breda and Ansaldo and after the First World War Henschel supplied a larger number as reparation, which had three-axle tenders instead of four. A total 470 were made by 1923.

Like the 730, they could be used freely due to their low axle load and could also pull passenger trains if necessary. Officially they were approved for a speed of 65 km/h, but could also reach up to 80 km/h. Seven were rebuilt to Caprotti valve gear, which was successful, but due to more difficult maintenance led to these locomotives being retired in the 1960s.

The rebuilds to Franco Crosti boilers, which was carried out on 175 locomotives, was more successful. These were divided into Grupo 743, which had a preheater on both sides of the boiler, and Grupo 741 with only one preheater under the boiler, which delivered the same power. Both the rebuilt and non-rebuilt ones survived until the end of the steam age on the FS in the seventies. Some were even kept as reserves until the early nineties. A total of 49 were preserved, three of which are still operational.

The class 835 was the standard steam shunter used by the Italian State Railways from 1906 for many decades. They were based on the classes 829 and 830 which originated in the Rete Mediterranea. The class 835 still had a saturated boiler and the 0-6-0T wheel arrangement. The first 97 built by Breda only had a steam brake for the locomotive, only the later ones had an air brake for the train.

By 1922, a total of 370 had been produced by Breda, Ansaldo, Reggiane and Officine Meccaniche. They could be found in stations and yards all around Italy and got the nickname “Cirilla”. Their number started to dwindle in the fifties and sixties when their frames, axles and coupling rods were used to create 60 electric shunters of the classes E.321 and E.322 and 29 diesel shunters of the class D.234. Nevertheless the last ones were used until 1984 and 54 were preserved.

The FS class 980 was a rack locomotive built starting in 1908 for standard-gauge lines. The first four were ordered from the SLM for the line to Volterra in Tuscany with an incline of ten percent. In 1912 and 1913, SLM delivered eight more for the Paola-Cosenza line in Calabria.

They were designed after the Winterthur system that combines the adhesion and rack drive with compound working. This meant that the high pressure cylinders were at the bottom and drove the wheels, while the low pressure cylinders at the top drove the crank axle for the rack drive. The crank axle worked onto the rack wheels via a 1 to 2,4 reduction gear, what meant that the low pressure cylinders moved at more than twice the speed of the high pressure cylinders, enabling all to be of the same size.

At Volterra, the last stretch with rack operation was closed in 1958. On the Paola-Cosenza line, new vehicles first took over passenger and later also freight traffic. Only 980.002 was preserved and can be found in the Museum of Pietrarsa. The class 981 was a superheated successor of the 980 that was built by Italian manufacturer Breda.

When in the early 1920s, the existing six-coupled express locomotives of the FS could no longer provide sufficient adhesive weight on hilly routes, the FS was one of the first railway companies in Europe to develop an eight-coupled express locomotive. This was the only way to comply with the maximum axle load of 17 tonnes that applied on hilly routes such as those in the Rome and Florence area. It was based on the 2-6-2 locomotive of the class 680 and added another coupled axle. 

While up to this point engines based on the Plancher system were preferred for four-cylinder compound locomotives in Italy, here the system according to von Borries, which was also used in Germany, was used. There were thus two inside high-pressure cylinders and two outside low-pressure cylinders, all of which acted on the third coupled axle. In order to create space for the connecting rods of the inner cylinders, the cylinders were arranged somewhat higher and inclined, and the second coupling axle was slightly cranked.

In contrast to the bar frame, which was very popular with express locomotives on the European mainland at the time, a plate frame with a thickness of 30 mm was used here. The leading axle with a lateral play of 94 mm was combined with the first coupled axle to form a Zara bogie and gave it a play of 20 mm. Due to the large grate area, the trailing axle was further away from the last coupled axle and therefore had a lateral play of 140 mm.

The production initially consisted of 40 engines that were supplied by Breda and had Heusinger valve gear. Another 20 pieces came from Ansaldo and received a Caprotti valve gear. These were initially designated class 477 and redesignated 746.100 in 1929. After their original routes were electrified, the locomotives were re-stationed once each in 1935 and 1937. They eventually landed in Sicily and were retired by 1967. Today only the 746.038 survives and is located in Milan, where it was once made.