40 to 50 hp
This opposed-piston engine has eight cylinders, eight pistons, but only four combustion chambers. You can think of the left and right half as being two 20o V-4 which share combustion chambers. There are two crank shafts/propeller drives on the left and right side of the engine. The two crank shafts are connected by the large transverse shaft you see outside of the engine. The cams for the value lifter are located at the center of this transverse shaft. On this engine two magnetos are also driven by this shaft. There are two other accessories geared to this shaft, most likely coolant and/or oil pumps.
The N.3 engine had a 2.95 in bore and a 5.91 in stroke with a displaced of 324 in3 It produced 40 hp at 1,200 rpm and 50 hp at 1,600 rpm weighting 198 lb.
In 1911 the SPA-Faccioli N.3 engine was installed in the the Faccioli N.4 aircraft. The Faccioli N.4 aircraft was originally powered by the SPA-Faccioli N.2, a 25 hp single cylinder engine two piston engine.
Italian Air Force Museum, Bracciano, Italy, Jan 2015
Some information from Jane's all the World's Aircraft 1910.
