Ford first introduced the 4.0-liter single-overhead-cam (SOHC) engine in 2001, as a replacement for the over-head-valve (OHV) 4.0-liter. Only the Ranger and Explorer made use of this engine, from 2001 through 2004. In 2005, the Mustang, a staple in Ford’s lineup, dropped the 3.8-liter engine in favor of this 4.0 liter. These three vehicles ran with the 4.0 liter through 2010; in 2011 the Mustang and Explorer switched to newer, more powerful, engines, but the 2011 Ranger makes use of the 4.0-liter SOHC.
The 4.0-liter SOHC engine–a V-6 engine–has a bore (cylinder width) of 3.95 inches and a stroke (the distance the piston travels inside the cylinder) of 3.32 inches. The bore and stroke combine to create a total engine displacement of 245 cubic inches. The 4.0 liter has a compression ratio ranging from 9:1 to 9.7:1, depending on the year and model of vehicle. The total valve count of 12 means that there are two valves per cylinder, one intake and one exhaust.