Ford flathead V8 engine, modified for power, depicted on cover of Hot Rod magazine. The "flat head" is evident.

Flathead engine or Sidevalve engine (sometimes called a flatty) refers to an internal combustion engine with valves placed in the engine block beside the piston, instead of in the cylinder head, as in an overhead valve engine. The design was common on early engine designs, but has since fallen from use. Cover of Hot Rod magazine, showing Ford Flathead V8 engine modified for power, uploaded by Gerald Zuckier. ... Cover of Hot Rod magazine, showing Ford Flathead V8 engine modified for power, uploaded by Gerald Zuckier. ... This article or section does not adequately cite its references or sources. ... A poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. ... piston + connecting rod Components of a typical, four stroke cycle, DOHC piston engine. ... The cylinder head from a GMC van. ... A cylinder head containing two overhead camshafts, one above each of the two valves In automotive engineering, an overhead valve internal combustion engine is one in which the intake and exhaust valves and ports are contained in the cylinder head. ...

Advantages

Generally the flathead uses a small chamber on one side of the cylinder to carry the valves. This has a number of advantages, primarily making the cylinder head much simpler. It also means a valve can be operated by pushing directly up on it, as opposed to needing some sort of mechanical arrangement to push it down or to drive overhead cams, as on a "valve-in-head" engine. It may also lead to slightly easier cooling, as valve and pushrods are out of the way of the cylinder, making a cooling jacket simpler to construct (but see below). The line of intakes along the side of the engine leads to the alternate name L-block (or L-head), due to the cylinders having the shape of an upside-down L. This configuration is also known as sidevalve. A cylinder head containing two overhead camshafts, one above each of the two valves In automotive engineering, an overhead valve internal combustion engine is one in which the intake and exhaust valves and ports are contained in the cylinder head. ... A pushrod or overhead valve (OHV) type piston engine places the camshaft below the pistons and uses pushrods or rods to actuate lifters or tappets above the cylinder head to actuate the valves. ... Ford sidevalve engine in a Ford model T. Ford Sidevalve is an engine from Ford Motor Company. ...

Disadvantages

On the downside, the flathead also requires the airflow to make at least a 90-degree turn to enter the cylinder, which makes it less efficient, colloquially called poorer "breathing". Breathing was not greatly important for early production cars because engines could not run long and reliably at high speed, and all engines had poor combustion anyway, so this was a minor concern given the benefits in simplicity.

A more serious concern is exhaust, which often follows a more complicated path to leave the engine. This virtually guarantees the engine will overheat under sustained steady heavy use. It is sometimes possible to arrange the engine layout so the exhaust will be taken through a second set of similar chambers moved to the other side of the cylinder, in which case the layout is referred to as a T-block.

History and applications

Although flathead in-line 4 and 6 cylinder engines were frequently used for automobiles, tractors, etc., the best known flathead automotive engine is the early 20th century Ford V-8, which has both sets of valves (intake and exhaust) located on the inside of the "Vee," and which are all operated by a single camshaft located above the crankshaft. Supercharged Flathead V8 Engine block of a Flathead V8 showing the location of the valve ports (the holes above the large cylinder bores) Ford flathead V8 engine, modified for power, on cover of Hot Rod magazine. ... Computer animation of a camshaft The camshaft is an apparatus often used in piston engines to operate poppet valves. ... Crankshaft (red), pistons (gray) in their cylinders (blue), and flywheel (black) Continental engine marine crankshafts, 1942 Components of a typical, four stroke cycle, DOHC piston engine. ...

Due to the heating and efficiency problems, flathead engines fell from "high power" uses such as aircraft engines fairly quickly, prior to World War I, though they were the basis of many early racing engines, including famous names such as Ardun (Zora Arkus-Duntov) and Frontenac (Louis Chevrolet). However they lived on for some time in the automotive world and were used on the Jeep for instance. Flatheads are no longer in common use for automobiles, although they are still used for some small-engine applications like lawnmowers. Because of their design, the size of valves and the compression ratio are limited, which in turn reduces available power and economy. To meet Wikipedias quality standards, this article or section may require cleanup. ... Combatants Allied Powers: Russian Empire France British Empire Italy United States Central Powers: Austria-Hungary German Empire Ottoman Empire Bulgaria Commanders Nikolay II Aleksey Brusilov Georges Clemenceau Joseph Joffre Ferdinand Foch Robert Nivelle Herbert H. Asquith D. Lloyd George Sir Douglas Haig Sir John Jellicoe Victor Emmanuel III Luigi Cadorna... Auto racing (also known as automobile racing or autosport) is a sport involving racing automobiles. ... Zora Arkus-Duntov (born December 25, 1909 - April 21, 1996), Belgian-born U.S. engineer. ... Frontenac can refer to: Frontenac, Missouri, United States of America Frontenac, Gironde, France Frontenac, Lot, France Louis de Buade de Frontenac, Governor of New France Château Frontenac, a building in Quebec City Frontenac County, Ontario, Canada Frontenac County, Quebec, Canada Frontenac, Quebec Fort Frontenac, where the city of Kingston... Louis Chevrolet Memorial, Indianapolis Speedway. ... Jeep is an automobile marque (and registered trademark) of DaimlerChrysler. ... Karl Benzs Velo (vélo means bicycle in French) model (1894) - entered into the first automobile race 2005 MINI Cooper S. An automobile (also motor car or simply car) is a wheeled passenger vehicle that carries its own motor. ... Bold text The compression ratio is a single number that can be used to predict the performance of any engine (such as an internal-combustion engine or a Stirling Engine). ...

Harley-Davidson motorcycle flathead engines

The flathead engine saw service Harley-Davidson motorcycles beginning with the "sport" model opposed twin produced from 1919-1923, and continuing in 1924 with single cylinder export 350cc and 500cc singles and continued in the Servicars until the 1970s. In the domestic U.S. market, the DL model, 1929-36, started Harley's side valve tradition in the 45 cubic inch displacement. The DLs featured a total loss oiling system (oil's always clean!), and were succeeded in 1937 by the WL, which had recirculating oil. The WL went on to serve in WWII as the U.S. and Canadian Army's primary two wheeled mount and subsequently as a civilian middleweight through 1952. The engine continued virtually unchanged with the GA designation in the three wheeled Servicar until production ceased in 1976. Logo on a 2003 Harley Davidson The Harley-Davidson Motor Company (NYSE: HDI) is a manufacturer of motorcycles based in Milwaukee, Wisconsin. ... Motorcyclists take a break from the road A motorcycle or motorbike is a single-track, two-wheeled motor vehicle powered by an engine. ... The 1970s decade refers to the years from 1970 to 1979, inclusive. ...

In 1952, the W series was supplanted by the K series flatheads, designed to compete with British sporting motorcycles of the time, as the American motorcycle Association allowed the 750cc sidevalvers to compete against 500cc overhead-valve bikes. The K models featured unit construction engine and transmission cases, right side foot shift and left side foot brake, and evolved from 45 cubic inches to 55 cubic inches over the short life of the retail market run. The K series was replaced by the overhead valve Sportster series in the retail market in 1957. However, racing versions of the K model continued to be produced in very limited numbers for some time after, winning both roadraces and dirt track through 1969, when the American Motorcycle Association decided to change the rules and make the venerable flatheads uncompetitive. The K racers were replaced first by the iron XR 750cc overhead valve engine, and two years later by the alloy head XR, which continues in service in flat track racing to this day.

In 1930, the 74 cubic inch VL flathead replaced the JD, which featured intake over exhaust (IoE) valve configuration. The VL had a single downtube frame and total loss oiling, culminating in an 80 cubic inch version in 1936. In 1937, the engine was given the U designation and went into the same frame and running gear configuration as the overhead valve Knucklehead, which originated in 1936. The U continued to be produced, in varying configurations as both a 74 cubic inch and 80 cubic inch motor through 1948. By that time, the first year of the Panhead, it had been thoroughly superseded and outsold in the marketplace by the superior performance of the overhead valve model big twins.

Harley-Davidson engine timeline

Flathead: 1929–1936 *Big twins until 1948 commercial market as models UL and ULH, WL 45 cubic inch until 1952-some literature indicating existence up to 1952 engine serial numbers displayed at motorcycle shows, old dealer catalog showed as optional engine until 1952 for limited market- sidecar use or military/ government contract completion . K models 1956 - was model prior to OHV CH /sportster. KRs made/raced even later. Servicar/'trike' noted preceding sentence to 1970s. RN*
Knucklehead: 1936–1947
Panhead: 1948–1965
Shovelhead: 1966–1985
Evolution: 1984–1999
Twin Cam 88: 1999—
Revolution: 2002—
1929 (MCMXXIX) was a common year starting on Tuesday (link will take you to calendar). ... 1936 (MCMXXXVI) was a leap year starting on Wednesday (link will take you to calendar). ... The knucklehead was an early Harley-Davidson motorcycle engine, so named because of the distinct shape of the rocker covers. ... 1947 (MCMXLVII) was a common year starting on Wednesday (the link is to a full 1947 calendar). ... Panheads are fans of the rock band Skillet. ... 1948 (MCMXLVIII) was a leap year starting on Thursday (the link is to a full 1948 calendar). ... 1965 (MCMLXV) was a common year starting on Friday (the link is to a full 1965 calendar). ... 1966 (MCMLXVI) was a common year starting on Saturday (the link is to a full 1966 calendar). ... 1985 (MCMLXXXV) was a common year starting on Tuesday of the Gregorian calendar. ... 1984 (MCMLXXXIV) was a leap year starting on Sunday of the Gregorian calendar. ... 1999 (MCMXCIX) was a common year starting on Friday, and was designated the International Year of Older Persons by the United Nations. ... For album titles with the same name, see 2002 (album). ...

See also

Logo on a 2003 Harley Davidson The Harley-Davidson Motor Company (NYSE: HDI) is a manufacturer of motorcycles based in Milwaukee, Wisconsin. ... The IOE (intake over exhaust) engine, also known as F-head and pocket valve, is a 4-stroke internal combustion type of primitive design. ... The knucklehead was an early Harley-Davidson motorcycle engine, so named because of the distinct shape of the rocker covers. ... Panheads are fans of the rock band Skillet. ... The Shovelhead was an air-cooled, 45 degree, V-twin motorcycle engine manufactured from 1966 to 1984 by the Harley Davidson Motor Company. ... The Evolution engine (aka Evo and Blockhead) was an air-cooled, 45 degree, V-twin motorcycle engine manufactured since 1984 by the Harley Davidson Motor Company. ... Please wikify (format) this article or section as suggested in the Guide to layout and the Manual of Style. ...

External link

• Images of each style of Harley-Davidson engine
• [http://www.harleykrxlrtt.com