Alessandro Anzani developed the first two-row radial from his earlier 3- cylinder Y engine by merging two onto the same crankshaft with a common crankweb.

The engine therefore had a lot in common with the early 3-cylinder motors: cylinders were a single iron casting with built-in valve cells and ribs, and pistons were steel with cast-iron rings.

By the end of 1912,[2] as with the smaller engines the exhaust valves were moved to the cylinder heads and operated by push-rods and rockers.

The exhaust valves were at the front of the engine, with the fuel inlet manifold at the rear.

[2] The engine used a single, kinked crankweb, coupled to slim but broad connecting rods in order to minimise the axial displacement between the two rows.