Isotta Fraschini V.6

V.6
Type	Piston aero engine
Manufacturer	Isotta Fraschini
First run	1917

The Isotta Fraschini V.6 was an Italian six-cylinder, water-cooled, in-line piston aero engine of the late World War I period, the "V" denoted "Volo" or "flight". Its construction was fairly typical of contemporary aircraft engines, using six cast-iron cylinders mounted in pairs with common heads.

Data from Gunston.

...
Wikipedia