The Continental PC-60 is a four-cylinder, horizontally opposed, air-cooled, 201 cubic-inch industrial gasoline engine, rated at 70 hp (at 2400 rpm). It was used mostly by the U.S. Air Force as a stationary power source and also as a forklift engine. For the most part, it’s a spinoff of the Continental C-90 aero engine.
The five major ways a PC-60 differs from a C-90:
1.It is skid-mounted rather than firewall-mounted.
2.The intake ports are on the top of the cylinders like on a Rolls-Royce O-200 cylinder.
3.The carburetor is mounted on top of the engine.
4.One hole in the crankshaft flange is offset to match a flywheel, not a prop.
5.It uses a single spark plug per cylinder with a single Slick 47-1 magneto.
Otherwise it is mostly an early C-90.
full article link
http://www.eaa.org/experimenter/articles/2009-04_vp2.asp