{{short description|1950 4-cylinder piston engine}} {{Use American English|date=January 2025}} {{Use mdy dates|date=February 2026}} {{More citations needed|article|date=January 2025}} <!-- This article is a part of [[Wikipedia:WikiProject Aircraft]]. Please see [[Wikipedia:WikiProject Aircraft/page content]] for recommended layout. --> {{infobox aero engine | name = McCulloch O-100 | image = File:McCulloch O-100-1.jpg | caption = McCulloch O-100-1 on display at [[Texas Air Museum - Stinson Chapter]] |engine_type= [[Piston engine]] horizontally opposed |manufacturer= [[McCulloch Aircraft Corporation]] [[McCulloch Motors Corporation]] |national_origin= United States |first_run= 1949 |major_applications= Benson B-8M autogyros; Radioplane Model PR-15 (OQ-6) and MQM 33 (Q-19); Model O-15-3 Righter Mfr. Co.<ref>{{Cite web|url=https://www.wingsofhistory.org/mcculloch-40-hp/|title=Wings of History Air Museum - McCulloch O-100-1 (model 4318A)|website=wingsofhistory.org|access-date=January 23, 2025}}</ref> |number_built= |developed_from= McCulloch 4 cylinder Model 4300C (O-90-1) 1945–1952 |developed_into= McCulloch 6 cylinder Model 6318 (O-150-2) 1955–1972 |variants_with_their_own_articles = }}

The '''McCulloch O-100''' is a four-cylinder, air cooled four piston drone engine developed by the McCulloch Aircraft Corporation (later to become the McCulloch Motors Corp.) which was founded 1943 in Milwaukee, Wisconsin and later moved to Los Angeles, California. The aircraft corporation was formed from the McCulloch Engineering Company.<ref>{{cite web |last=McCutcheon |first=Kimble D. |date=21 December 2014 |title= McCulloch Aircraft Engines |url=https://www.enginehistory.org/members/McCulloch |website=Aircraft Engine Historical Society |location=Huntsville, AL |access-date=January 21, 2025}}]</ref>

In 1972, the corporation was renamed McCulloch Motors Corp. of Los Angeles and sold to Northrop-Ventura.

==Development==

The McCulloch line of engines consisted of small 1, 2, 4 and 6 cylinder 2-stroke engines. The first engines were used for industrial motor pumps and chainsaws. In the 1940s, military contract started with a 4-cylinder model 4300 (Military O-88) engine to be used in aeronautical target drones. Later with bigger Horsepower (H.P.) development, the engines had experimental aircraft applications.<ref>{{Cite web|url=https://aeroenginesaz.com/en/brand_mcculloch/%22Aerospace|title=Aeroengines AZ {{pipe}}|website=www.aeroenginesaz.com}}</ref>

==Variants== ''Horizontally-Opposed Piston Engines''<ref>{{Cite web|url=https://aeroenginesaz.com/en/brand_mcculloch|title=McCULLOCH|website=www.aeroenginesaz.com}}</ref>

===4-Cylinder=== *Model 4300 (Mil O-88) *Model 4300C *Model 4318A (Mil O-100-1) *Model 4318B (mil O-100-2)

===6-Cylinder=== *Model 6318 (O-150-2) *Model TC-6150 (O-150-4)

==Display==

===Australia===

* [[Moorabbin Air Museum]] - Moorabbin Airport, Melbourne Australia<ref>{{Cite web|url=https://www.aarg.com.au/mcculloch.html|title=McCulloch 43180-100-1|website=Moorabbin Air Museum}}</ref>

===United States===

* Wings of History Air Museum - San Martin, California * [[Texas Air Museum - Stinson Chapter]] - San Antonio, Texas * [[Combat Air Museum]] - Topeka Regional Airport at Forbes Field, Topeka, Kansas

==Specifications (McCulloch O-100-1)== [[File:McCulloch O-100-1 (model 4318A) on display at the Wings of History Air Museum.jpg|thumb|McCulloch O-100-1 (model 4318A) on display at the Wings of History Air Museum]] {{pistonspecs <!-- If you do not understand how to use this template, please ask at [[Wikipedia talk:WikiProject Aircraft]] --> <!-- Please include units where appropriate (main comes first, alt in parentheses). If data are missing, leave the parameter blank (do not delete it). For additional lines, end your alt units with a right parenthesis ")" and start a new, fully formatted line beginning with an asterisk "*" --> |type=opposed (flat) 4-cylinder [[piston engine]] |ref=''McCulloch 4318 Engine Manual''<ref name="scribd">{{cite web|url=https://www.scribd.com/document/464274867/|website=scribd.com|title=Mcculloch 4318 Engine Manual|access-date=January 23, 2025}}</ref> |bore={{cvt|3+3/16|in|mm|1}} |stroke={{cvt|3+1/8|in|mm|1}} |displacement={{convert|100|in3|L|abbr=on}} |length={{convert|26|in|mm|abbr=on}} |diameter={{convert|27|in|mm|abbr=on}} |width= |height= |weight={{convert|83|lb|kg|abbr=on}} |valvetrain= |supercharger= |turbocharger= |fuelsystem= downdraft [[carburetor]] |fueltype=115/145 [[Octane rating|RON]] |oilsystem=[[Dry sump]] |coolingsystem=[[Air-cooled]] |power={{convert|72|hp|kW|abbr=on}} at 4,100 [[Revolutions per minute|rpm]] (takeoff) |specpower=0.66&nbsp;hp/in{{sup|3}} |compression=8:1 |fuelcon= |specfuelcon= |oilcon= |power/weight=0.82&nbsp;hp/lb }}

==See also== *[[List of aircraft engines]]

==References== {{Reflist}}

{{US military piston aeroengines}}

[[Category:1940s aircraft piston engines]]