Editing Flathead engine (section)

==History and applications==
The sidevalve arrangement was especially common in the United States and used for motor vehicle engines, even for engines with high specific power output.<ref name="Pischinger 1948_14" /> Sidevalve designs are still common for many [[small engine|small]] [[Single-cylinder engine|single-cylinder]] or [[Straight-twin engine|twin-cylinde]]r engines, such as [[lawnmower]]s, [[cultivator|rotavators]], [[two-wheel tractor]]s and other [[subsistence agriculture|basic farm machinery]].{{citation needed|date=January 2019}}<!--regular off-the-shelf lawn mowers (Honda for instance) have OHC engines-->

===Flathead cars===
Multicylinder flathead engines were used for cars such as the [[Ford Model T engine|Ford Model T]] and [[Ford Model A (1927–31)|Ford Model A]], the [[Ford flathead V8 engine]] and the [[Ford Sidevalve engine]]. [[Cadillac]] produced [[Cadillac V16 engine#Series 90|V-16 flathead engines]] for their [[Cadillac V-16#1938.E2.80.931940|Series 90 luxury cars]] from 1938 to 1940.<ref>{{cite web | url = http://www.hemmings.com/hcc/stories/2007/02/01/hmn_feature6.html | title = Reignmaker – 1939 Cadillac Series 39-90 | last = LaChance | first = David | date = February 2007 | website = Hemmings Motor News | publisher = American City Business Journals | access-date = 17 November 2015 | quote = Mechanically, the Series 90 cars shared the advances of the Series 75. The V-8 car's three-speed manual transmission was deemed up to the task of handing the torque of the V-16, in part because the larger engine delivered its impulses so smoothly.}}</ref> [[Packard]] and [[Pontiac straight-8 engine|Pontiac]] produced flathead inline 8-cylinder engines until 1954. Also in the British [[Morris Eight]], and [[Morris Minor]] series I.

After [[WWII]], flathead designs began to be superseded by OHV (overhead valve) designs. Flatheads were no longer common in [[automobile|cars]], but they continued in more rudimentary vehicles such as [[off-road vehicles|off-road]] [[Jeep|military Jeeps]]. In US [[custom car]] and [[hot rod]] circles, restored examples of early Ford flathead V8s are still seen.<ref name=AmericanRodder1994/><ref>''Street Rodder'', 1/85, p.72.</ref>

===Flathead aero-engines===
The simplicity, lightness, compactness and reliability might seem ideal for an [[aircraft engine|aero-engine]], but because of their low efficiency, early flathead engines were deemed unsuitable. Two notable exceptions were the American [[Aeronca E-107]] opposed twin [[aero engine]] of 1930 and the [[Continental A40]] flat four of 1931, which became one of the most popular light aircraft engines of the 1930s. Two modern flatheads are the Belgian [[D-Motor]] [[flat-four]]s and [[flat-six]]es.<ref>Although very small and compact, the D-Motor flat-six displaces nearly 4 litres.</ref> These are extremely [[oversquare]] and compact aero-engines with direct drive to a propeller.<ref>{{cite web |url=http://d-motor1.vpweb.be/Recent-information.html |title=Kapelstraat 198 8540 Deerlijk – Recent information |publisher=D-motor.eu |access-date=2011-12-06 |url-status=dead |archive-url=https://web.archive.org/web/20120328094443/http://d-motor1.vpweb.be/Recent-information.html |archive-date=March 28, 2012 |df=mdy-all }}</ref><ref name="WDLA15">Tacke, Willi; Marino Boric; et al: ''World Directory of Light Aviation 2015-16'', pages 256-257. Flying Pages Europe SARL, 2015. {{ISSN|1368-485X}}</ref>

===Flathead motorcycles===
{{main|Flathead motorcycles}}

Flathead designs have been used on a number of early pre-war motorcycles, in particular US V-twins such as [[Harley-Davidson]] and [[Indian Motocycle Manufacturing Company|Indian]], some British singles, [[History of BMW motorcycles|BMW]] [[flat twin]]s and Russian copies thereof.<ref>For example, some Dnepr and Ural used flathead designs that BMW had licensed to the Soviets.</ref> The [[Cleveland Motorcycle Manufacturing Company]] produced a T-head four-cylinder in-line motorcycle engine in the 1920s.
<gallery>
Image:1915 Cadillac Model 51 V8 4stroke engine photo2.JPG|1915 Cadillac flathead engine block
Image:flathead.jpg|Harley-Davidson flathead
Image:Indian Chief Black Hawk 80 cubic inch 1950.jpg|Indian Chief Black Hawk
Image:BMW motorbike R 12 (aka).jpg|BMW R12
Image:Cleveland Model 4-45 1927.jpg|Cleveland Model 4-45
</gallery>