Initially with a 1,987 cc (121.3 cu in) capacity (72.6 mm × 80 mm (2.86 in × 3.15 in), with a compression ratio of 13.5 :1) delivering 160 hp (120 kW), in 1951 and 1952
Then 1,988 cc (121.3 cu in) capacity (75 mm × 75 mm (2.95 in × 2.95 in), with a compression ratio of 13.5 :1, with twin ignition[clarification needed]) delivering 180 hp (130 kW), in late 1952
And finally with a 1,970 cc (120 cu in) capacity 76.2 mm × 72 mm (3.00 in × 2.83 in), with a compression ratio of 12 :1, with twin ignition[clarification needed]) delivering 197 hp (147 kW), in 1953.
The 3.0-liter (approx 245 bhp (183 kW) at 6200 rpm) engine used in the Maserati 300S was based on the Straight-6 design of the Maserati 250F and incorporated a lengthened stroke developed by Vittorio Bellentani to increase the capacity from the original 2.5-litres. The compression ratio was reduced from 12:1 to 9.5:1, partly due to the FIA regulations requiring the engine to be run on road car fuel. It used three Weber carburetors.[20][21][22][23][24][25][26]