Lycoming O-360 is a family of four-cylinder, direct-drive, horizontally opposed, air-cooled, piston aircraft engines. Engines in the O-360 series produce between 145 and 225 horsepower (109 to 168 kW), with the basic O-360 producing 180 horsepower. 
The engine family has been installed in thousands of aircraft, including the
Cessna 172, Piper Cherokee/Archer, Grumman Tiger, and many home-built types. It has a factory rated time between overhaul (TBO) of 2000 hours or twelve years.  O-360 family engines are also widely used in  airboats, most notably in the Hurricane Aircats used by the US Army during the Vietnam War. 
The first O-360 certified was the A1A model, certified on 20 July 1955 to United States CAR 13 effective March 5, 1952 as amended by 13-1 and 13-2.
The  Lycoming IO-390 is an O-360 which has had its cylinder bore increased by inch (4.76 mm), developing 210 hp (157 kW).  
The O-360 family of engines comprises 167 different models with 12 different prefixes. All have a 361-cubic-inch (5.92-liter) displacement and 5.125 and 4.375 in (130.2 and 111.1 mm)
bore and stroke.    
O-360 carbureted series
HO-360 horizontally mounted series for helicopter installation
LO-360 same as O-360, but with left-hand rotating crankshaft, for use in pairs on twin-engined aircraft 
TO-360 turbocharged series
LTO-360 turbocharged left-hand rotation series
IO-360 fuel-injected series
LIO-360 same as IO-360, but with left-hand rotating crankshaft
AIO-360 inverted mount (dry sump aerobatic) fuel-injected series
AEIO-360 aerobatic fuel-injected series
HIO-360 horizontally mounted fuel-injected series for helicopters
LHIO-360 left-hand rotation, fuel-injected, horizontally mounted for helicopters TIO-360 turbocharged and fuel-injected series
Piper PA-44-180 Seminole features two Lycoming O-360 engines
LIO-360 AIO-360 AEIO-360 HIO-360 LHIO-360
Data from Type Certificate Data Sheet E-286 
Fuel type: 91/96 avgas minimum grade 
Oil system: 8 US qt (8 l) wet sump Cooling system: air-cooled
Power output: 180 hp (134 kW) at 2700 rpm
8.5:1 Compression ratio: Fuel consumption: 7.8 US gal (30 L) to 9 US gal (34 L) per hour 
^ a b
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Enfield, Samuel; Burr, R.; Badgett, R.; et al., eds. (April 15, 1966). Airboats (PDF) (Technical report). San Francisco: Army Concept Team in Vietnam. p. 2. R-1590 0 – via DTIC.
^ a b c
Federal Aviation Administration (August 2009). "Type Certificate Data Sheet No. E-286 Revision 20" (PDF) . Retrieved 2011.
Lycoming Engines (n.d.). "Lycoming IO-390-X" . Retrieved .
Lycoming Engines (2004). "Specialty datasheet" (PDF) . Retrieved .
Federal Aviation Administration (10 January 2018). "Type Certificate Data Sheet No. 1E10 Revision 28" (PDF) . Retrieved 2019.
Federal Aviation Administration (March 1986). "Type Certificate Data Sheet No. E26EA Revision 4" . Retrieved .
Federal Aviation Administration (March 1986). "Type Certificate Data Sheet No. E16EA Revision 5" . Retrieved .
Federal Aviation Administration (13 July 2004). "Airplane Flying Handbook" (PDF). Archived from the original (PDF) on 21 September 2012 . Retrieved 2012.
Mooney Aircraft, Inc. (March 1967). Executive 21 Owners Manual.
^ a b
Federal Aviation Administration (February 2007). "Docket No. FAA-2006-25948; Directorate Identifier 2006-NE-32-AD; Amendment 39-14951; AD 2007-04-19". Archived from the original on 2011-07-13 . Retrieved .
Lycoming (2010). "Lycoming Service Instruction 1070Q" (PDF). Archived from the original (PDF) on 17 November 2011 . Retrieved 2011.
"O-360, HO-360, IO-360, AIO-360, HIO-360 & TIO-360 Operator's Manual". lycoming.com . Retrieved 2018.