{{Short description|American piston aircraft engine}} {{Use dmy dates|date=December 2022}} {{Use American English|date=December 2022}} <!-- This article is a part of [[Wikipedia:WikiProject Aircraft]]. Please see [[Wikipedia:WikiProject Aircraft/page content]] for recommended layout. --> {{infobox aero engine |name= O-175/4AC-176 |image = |caption = |engine_type= [[Piston]] [[aircraft engine]] |national_origin = United States |manufacturer= [[Franklin Engine Company]] |first_run= 1940 |major_applications= |number_built = |developed_from = |developed_into = |variants_with_their_own_articles = }}

The '''Franklin O-175''' (company designation '''4AC-176''') was an American air-cooled aircraft engine of the 1940s. The engine was of [[Flat-four engine|horizontally-opposed four-cylinder]] and [[Engine displacement|displaced]] {{convert|175|cuin|L|1|abbr=on}}. The power output was nominally {{convert|80|hp|kW|abbr=on|0}}. A later variant was designated '''O-180''', despite sharing the same displacement.

A related four-cylinder engine of slightly smaller capacity was known as the '''O-170''' or '''4AC-171'''. It produced {{convert|60|hp|kW|abbr=on|0}}.

==Variants== ===O-170=== ;4AC-171:{{convert|60|hp|kW|abbr=on|0}}

===O-175=== ;4AC-176: ::'''4AC-176-B''' - 65 hp (48 kW) at 2,200 rpm ::'''4AC-176-BA/(O-175-1)''' - 65 hp (48 kW) at 2,300 rpm ::'''4AC-176-C''' - 75 hp (56 kW) at 2,500 rpm ::'''4AC-176-D''' - 80 hp (60 kW) at 2,650 rpm ::'''4AC-176-F''' - 80 hp (60 kW) at 2,500 rpm ;4ACG-176

===O-180=== ;4AC-176-F3 (O-180-1)

==Applications== *[[Aeronca Chief family#Variants|Aeronca L-3D]] *[[Bowyer BW-1 flying wing]] *[[CAP-4 Paulistinha]] *[[Harris Little Jewel]] *[[Interstate Cadet]] *[[IPT-7 Junior]] *[[Jensen Sport]] (O-170) *[[Johnson-Funke monoplane]] *[[Langley Twin]] *[[Piper J-3 Cub]] *[[Piper J-4]] *[[Piper L-4]] *[[Porterfield Collegiate]] *[[Taylorcraft B|Taylorcraft BF-60]] (O-170) *[[Taylorcraft B|Taylorcraft BF-65]]

==Specifications (4AC-176-BA2, O-175-1)== {{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 </li> and start a new, fully formatted line with <li> --> |ref=Wilkinson<ref name=Wilkinson>{{cite book|last=Wilkinson|first=Paul H.|title=Aircraft Engines of the world 1945|year=1945|publisher=Paul H. Wilkinson|location=New York|pages=88–89}}</ref> |type=4-cylinder air-cooled [[horizontally opposed]] aircraft piston engine |bore={{convert|4|in|mm|abbr=on|0}} |stroke={{convert|3.5|in|mm|abbr=on|0}} |displacement={{convert|176|cuin|L|abbr=on|2}} |length={{convert|28.6|in|mm|abbr=on|0}} |diameter= |width={{convert|30.2|in|mm|abbr=on|0}} |height={{convert|20|in|mm|abbr=on|0}} |weight={{convert|182|lb|kg|abbr=on|1}} |valvetrain=OHV, 1x inlet valve, 1x exhaust valve operated by pushrods |supercharger= |turbocharger= |fuelsystem=1x Marvel-Schebler MA-3P updraught carburetor |fueltype=73 octane gasoline |oilsystem=Pressure system at {{convert|40|psi|bar|abbr=on|0}}, [[wet sump]] |coolingsystem=Air-cooled |power={{convert|65|hp|kW|abbr=on|1}} at 2,300 rpm for take-off |specpower= 0.37 hp/(cu in) (16.837 kW/L) |compression=6:1 |fuelcon= |specfuelcon= 0.49 lb/(hp h) (0.298 kg/(kW h), 220 US gal/(hp h)) cruising |oilcon=0.003 lb/(hp h) (0.0018 kg/(kW h), 1.4 US gal/(hp h)) cruising |power/weight=0.357 hp/lb (0.587 kW/kg)

|designer= |reduction_gear=

|general_other= |components_other= |performance_other= }}

==See also== {{aircontent <!-- include as many lines are appropriate. additional lines/entries with carriage return. --> |see also= |related= |similar engines= |similar aircraft=<!-- similar or comparable aircraft --> |lists=<!-- related lists --> *[[List of aircraft engines]] }}

==References==

;Notes {{reflist}} ;Bibliography {{refbegin}} * Gunston, Bill. (1986) ''World Encyclopedia of Aero Engines''. Patrick Stephens: Wellingborough. p.&nbsp;57 {{refend}}

{{Franklin aeroengines}} {{US military piston aeroengines}}

[[Category:Franklin aircraft engines]] [[Category:1940s aircraft piston engines]] [[Category:Boxer engines]] [[Category:Four-cylinder engines]] [[Category:Air-cooled aircraft piston engines]]