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Encyclopedia > Overhead valve
Components of a pushrod valve actuation system
Components of a pushrod valve actuation system
Picture of an engine block, showing the camshaft, pushrods, and rockers.
Picture of an engine block, showing the camshaft, pushrods, and rockers.

An overhead valve (OHV) engine, also called pushrod engine or I-head engine is a type of piston engine that places the camshaft in the cylinder block (usually beside and slightly above the crankshaft in a straight engine or directly above the crankshaft in the V of a V engine) and uses pushrods or rods to actuate rocker arms above the cylinder head to actuate the valves. Lifters or tappets reside in the engine block between the camshaft and pushrods. Off Highway Vehicle is a vehicle registration class including all terrain vehicles (ATVs), off-highway motorcycles (OHMs) and off-road vehicles (ORVs), such as 4x4 trucks or Jeeps. ... Image File history File links Question_book-3. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links Metadata Size of this preview: 450 × 600 pixelsFull resolution (480 × 640 pixel, file size: 101 KB, MIME type: image/jpeg) (All user names refer to en. ... Image File history File links Metadata Size of this preview: 450 × 600 pixelsFull resolution (480 × 640 pixel, file size: 101 KB, MIME type: image/jpeg) (All user names refer to en. ... Components of a typical, four stroke cycle, DOHC piston engine. ... For the fictional characters of the same name, see Camshaft (Transformers). ... The cylinder block of a Ford I4 DOHC engine The cylinder block or engine block is a machined casting (or sometimes an assembly of modules) containing cylindrically bored holes for the pistons of a multi-cylinder reciprocating internal combustion engine, or for a similarly constructed device such as a pump. ... 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. ... Usually found in 4 and 6 cylinder configurations, the straight engine (often designed as inline engine) is an internal-combustion engine with all cylinders aligned in one row, with no or only minimal offset. ... A V engine is a common configuration for an internal combustion engine. ... The cylinder head from a GMC van. ... 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. ... In mechanical engineering, a tappet is a projection which imparts a linear motion to some other component within an assembly. ...


This contrasts with an overhead cam (OHC) design which places the camshafts above the cylinder head and drives the valves directly or through short rocker arms. In an OHC engine, the camshafts are normally part of the cylinder head assembly, while in an I-head engine the camshaft (rarely more than one) is part of the main engine block assembly. Overhead cam (OHC) piston engines place the camshaft above the cylinder heads and drive the valves or lifters directly instead of using pushrods. ...


In 1949, Oldsmobile introduced the Rocket V8. It was the first high-compression I-head design, and is the archetype for most modern pushrod engines. General Motors is the world's largest pushrod engine producer with engines such as the 3800 Series III Supercharged V6 (260 hp, 280 lbf·ft torque), LS7 Chevrolet Corvette 7.0 L V8 Engine (505 hp, 475 lbf·ft torque) and LS4 5.3 L DOD V8 (303 hp, 323 lbf·ft torque). Few pushrod type engines remain in production. This is a result of few manufacturers wanting to design both OHV and OHC engines, and competitively OHC racing engines have an advantage in power due to rpm limits. However, in 2002, Chrysler introduced a new pushrod engine: a 5.7L Hemi engine. The new Chrysler Hemi engine presents advanced features such as variable displacement technology and has been a popular option with buyers. The Hemi was on the Ward's 10 Best Engines list for 2003 through 2007. Oldsmobile was a brand of automobile produced for most of its existence by General Motors. ... This article does not cite any references or sources. ... General Motors Corporation, also known as GM or The General, an American multinational conglomerate corporation, is the worlds largest auto company by annual production volume for 2006, and the second largest by sales volume as of the first half of 2007, behind Toyota Motor Corporation. ... The Buick V6 engine family, initially marketed as the Fireball at its introduction in 1962, is a large V6 engine used by General Motors. ... For other meanings, see supercharger (disambiguation) A supercharger (sometimes called a blower), a positive displacement or centrifugal pump, is a gas compressor used to pump air into the cylinders of an internal combustion engine. ... The foot-pound force (symbol: ft·lbf) is an English unit of work or energy. ... The LS is Generation III and Generation IV, the latest evolution of General Motors line of small-block V8 engines. ... The Chevrolet Corvette is a sports car that has been manufactured by Chevrolet since 1953. ... The LS is Generation III and Generation IV, the latest evolution of General Motors line of small-block V8 engines. ... Active Fuel Management (formerly known as Displacement on Demand) is a trademarked name for the automobile variable displacement technology from General Motors. ... Early Hemi in a 1957 Chrysler 300C. A Chrysler Hemi engine is one of three different internal combustion engine families from Chrysler that are Hemi engines; in other words, they utilize a hemispherical combustion chamber. ... Variable displacement is an automobile engine technology that allows the engine displacement to change for improved fuel economy. ... Wards 10 Best Engines is an annual list of the ten best automobile engines selected by Wards AutoWorld magazine. ...

Contents

History

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. Automotive engineering is a branch of Vehicle engineering, incorporating elements of mechanical, electrical, electronic, software and safety engineering as applied to the design, manufacture and operation of automobiles, buses and trucks and their respective engineering subsystems. ... The internal combustion engine is an engine in which the combustion of fuel and an oxidizer (typically air) occurs in a confined space called a combustion chamber. ... 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. ... The cylinder head from a GMC van. ...


The original overhead valve or OHV piston engine was developed by the Scottish-American David Dunbar Buick. It employs pushrod-actuated valves parallel to the pistons and this is still in use today. This contrasts with previous designs which made use of side valves and sleeve valves. Components of a typical, four stroke cycle, DOHC piston engine. ... Scottish Americans or Scots Americans are citizens of the United States whose ancestry originates in the northwest European nation of Scotland. ... David Dunbar Buick David Dunbar Buick (September 17, 1854 - March 5, 1929) was a Scottish-American inventor best known for founding the Buick Motor Company. ... A pushrod engine or overhead valve (OHV) engine is a type of piston engine that places the camshaft below the pistons (usually beside and slightly above the crankshaft in a straight engine or directly above the crankshaft in the V of a V engine) and uses pushrods or rods to... Parallel is a term in geometry and in everyday life that refers to a property in Euclidean space of two or more lines or planes, or a combination of these. ... For the American composer, see Walter Piston. ... It has been suggested that this article or section be merged with pushrod engine. ... piston engine Bristol Perseus The sleeve valve is a type of valve mechanism for piston engines which have traditionally relied on the more common poppet valve. ...


Nowadays, side-valves have virtually disappeared (except perhaps in lawn-mower engines) and valves are almost all "overhead". However most are now driven more directly by the overhead camshaft system and these are designated OHC instead (either SOHC or DOHC). A cylinder head sliced in half shows two overhead camshafts—one above each of the two valves. ... A cylinder head sliced in half shows two overhead camshafts—one above each of the two valves. ... A cylinder head sliced in half shows two overhead camshafts—one above each of the two valves. ...


Pushrod engines have become less common in recent years, serving primarily as either truck engines or as budget V6 models for General Motors, though Chrysler's HEMI engines and GM's LS series are a notable exception. Pushrod engines are nearly extinct among other automakers.


Advantages

In contrast, pushrod engines have specific advantages:

  • Smaller overall packaging - Because of the camshaft's location inside the engine block, pushrods are more compact than an overhead cam engine of comparable displacement. For example, Ford's 4.6 L OHC modular V8 is larger than the 5.0 L I-head Windsor V8 it replaced. GM's 4.6 L OHC Northstar V8 is slightly taller and wider than GM's larger displacement 5.7 to 7.0 L I-head LS V8. The Ford Ka uses the venerable Kent Crossflow pushrod engine to fit under its low bonnet line.
  • Less complex drive system - Pushrod engines have a less complex drive system when compared with OHC engines. Most OHC engines drive the camshaft or camshafts using a timing belt, a chain or multiple chains. These systems require the use of tensioners which add some complexity to the engine. In addition, failure of the timing belt or chain can sometimes result in the pistons colliding with the open valves, resulting in severe damage to the engine.
  • Reduced major servicing times - Operations which require the cylinder head to be removed (such as head gasket replacement) can be performed without removal of the camshaft and therefore the camshaft drive does not need to be replaced or re-timed, saving both time and expense. If the head and block are cast iron, this can be achieved very quickly as full cooling of the parts may not be necessary.

It has been suggested that this article or section be merged with pushrod engine. ... Ford may mean a number of things: A ford is a river crossing. ... The Modular engine, or mod motor as it is often referred to, is Ford Motor Companys modern overhead camshaft (OHC) V8 and V10 engine family. ... The Windsor engine is a 90-degree small-block V8 from Ford Motor Company. ... Northstar is Cadillacs name for its DOHC V8 engine. ... The LS is Generation III and Generation IV, the latest evolution of General Motors line of small-block V8 engines. ... This article does not cite any references or sources. ... Overhead cam (OHC) piston engines place the camshaft above the cylinder heads and drive the valves or lifters directly instead of using pushrods. ... Overhead cam (OHC) piston engines place the camshaft above the cylinder heads and drive the valves or lifters directly instead of using pushrods. ... For the fictional characters of the same name, see Camshaft (Transformers). ... For the fictional characters of the same name, see Camshaft (Transformers). ... Timing belt A timing belt, timing chain or cam belt is a part of an internal combustion engine that controls the timing of the engines valves. ... Roller chain and sprocket Roller chain or bush roller chain is the type of chain most commonly used for transmission of mechanical power on bicycles, motorcycles, and in industrial and agricultural machinery. ... Roller chain and sprocket Roller chain or bush roller chain is the type of chain most commonly used for transmission of mechanical power on bicycles, motorcycles, and in industrial and agricultural machinery. ... Cast iron usually refers to grey cast iron, but can mean any of a group of iron-based alloys containing more than 2% carbon (alloys with less carbon are carbon steel by definition). ...

Limitations

Two specific problems remain with pushrod engines:

  • Limited engine speeds or rpm - Pushrod engines have more valvetrain moving parts (the pushrod itself) thus more valvetrain inertia, suffer more easily from valve "float" due to the innate valve actuation rocker design, and exhibit a tendency for the pushrods, if too long, to flex or snap at very high engine speeds. Therefore, a pushrod engine cannot revolve ("rev") at engine speeds as near as high as an OHC design. Modern pushrod engines are usually limited to 6,000 rpm. Compare this to modern OHC engines that have rev limits from 6,000 rpm to 9,000 rpm, while rev limits near 20,000 rpm are for Formula One racing engines. High-revving pushrod engines have also been developed, albeit solid (mechanical) lifter designs, flat and roller. In 1969, Chevrolet offered a Corvette, Camaro Z28, and other models with a solid lifter cam pushrod V8, the ZL1, that could rev to 8,000 rpm. The Volvo B18 and B20 engines can rev to more than 7,000 rpm with their solid lifter camshaft. However, the LS7 of the C6 Corvette Z06 is the first production hydraulic roller cam pushrod engine to have a redline of 7100 rpm. Various pushrod racing engines are capable of varying from 9,000 to 10,500 rpm.
  • Limited cylinder head design flexibility - The biggest benefit that an OHC design has is the ease of using multiple intake and exhaust valves and variable valve timing. Most modern pushrod engines have two valves per cylinder, while many OHC engines can have three, four or even five valves per cylinder to achieve greater efficiency and power. Recently, however, GM has begun offering a pushrod V6 with VVT, and Cummins' ISB is a 4-valve pushrod straight-6. The GM 3900 was the first mass-produced pushrod engine to feature variable valve timing. The system adjusts both intake and exhaust timing between only two settings, it can not vary the intake and exhaust timing independently. Presently there is even a company called Arao Engineering, formerly Dominion Performance, that has developed, patented, and sold a 4-valve per cylinder aluminum cylinder head for various pushrod engines like the small/big block Chevrolet engines, Ford small/big block engines and others.

For other uses, see Revolutions per minute (disambiguation). ... “F1” redirects here. ... Chevrolet (IPA: - French origin) (colloquially Chevy) is a brand of automobile, produced by General Motors (GM). ... Modified 1969 Chevrolet Camaro. ... This Volvos litre inline-4 OHV gasoline engine was used from 1961 to 1968 in the Volvo PV544, 120 (Amazon), P1800 and 140 series automobiles. ... In automotive engineering, an engine is referred to as multi-valve (or multivalve) when each cylinder has more than two valves. ... Variable valve timing, or VVT, is a generic term for an automobile piston engine technology. ... Variable valve timing, or VVT, is a generic term for an automobile piston engine technology. ... This article is about the diesel engine manufacturer. ... The Cummins B Series is a family of straight-4 and straight-6 diesel truck and industrial piston engines. ... The straight-6 (also inline 6, I-6, or I6) is an internal combustion engine with six cylinders aligned in a single row. ...

1994 Mercedes/Ilmor Indianapolis 500 engine

The Indy 500 race in Indianapolis each year bears some vestige of its original purpose as a proving ground for automobile manufacturers, in that it once gave an advantage in engine displacement to engines based on stock production engines, as distinct from out-and-out racing engines designed from scratch. One factor in identifying production engines from racing engines was the use of pushrods, rather than the overhead cams used on most modern racing engines; Mercedes-Benz realized before the 1994 race that they could very carefully tailor a purpose-built racing engine using pushrods to meet the requirements of the Indy rules and take advantage of the 'production based' loophole but still design it to be state of the racing art in all other ways, without any of the drawbacks of a real production-based engine. They entered this engine in 1994, and, as expected, dominated the race. After the race, the rules were changed in order to reduce the amount of boost pressure allowed to be supplied by the turbocharger. The inability of the engine to produce competitive power output after this change caused it to become obsolete after just the one race. Mercedes-Benz knew this beforehand, deciding that the cost of engine development was worth one win at Indianapolis. The Indianapolis 500 is an American race for open-wheel automobiles held annually over the Memorial Day weekend at the Indianapolis Motor Speedway in Speedway, Indiana. ... The Indianapolis skyline Indianapolis is the capital of the U.S. state of Indiana. ... Year 1994 (MCMXCIV) The year 1994 was designated as the International Year of the Family and the International Year of the Sport and the Olympic Ideal by the United Nations. ... Air foil bearing-supported turbocharger cutaway made by Mohawk Innovative Technology Inc. ... Air foil bearing-supported turbocharger cutaway made by Mohawk Innovative Technology Inc. ...


Comparison of engine configurations and types

Comparing engines is not an exact science. This table shows the comparison of some of the most important features when looking at an engine

Engine name Capacity Geometry Type Car Engine weight Power RPM power Torque RPM torque Power/Weight
(liters) (application) (lb) (HP,SAE) (rpm) (lbf·ft) (rpm) (hp/lb)
F140 6.0 V12 DOHC 2002 Enzo Ferrari 496 660 7,800 485 5,500 1.33
13B-MSP (Renesis) 1.3 2-Rotor Wankel 2003 Mazda RX-8 180 238 8,500 159 5,500 1.32
M80 5.7 V10 DOHC 2005 Porsche Carrera GT 472 605 8,000 435 5,750 1.28
F130 4.7 V12 DOHC 1995 Ferrari F50 437 513 8,500 347 6,500 1.17
LS7 7.0 V8 pushrod 2006 Corvette Z06 458 505 6,300 470 4,800 1.10
AMG 6.3 6.2 V8 DOHC 2007 Mercedes CLK63 AMG 439 475 6,800 465 5,000 1.08
LS3 6.2 V8 pushrod 2008 Chevrolet Corvette C6 420 436 5,900 428 4,400 1.02
S85 5.0 V10 DOHC 2007 BMW M5 & BMW M6 529 500 7,750 383 6,100 0.94
SRT-10 8.3 V10 pushrod 2006 Dodge Viper 650 510 5,600 535 4,600 0.79
S62 5.0 V8 DOHC 2003 BMW M5 527 396 6,600 370 3,800 0.75

Comparison of naturally-aspirated engines for race and road legal track day cars This article is about the car. ... All Mazda Wankel rotary engines are essentially a single family - they all derive from the first Wankel experiments in the early 1960s. ... Wankel Engine in Deutsches Museum Munich, Germany The Wankel rotary engine is a type of internal combustion engine, invented by German engineer Felix Wankel, which uses a rotor instead of reciprocating pistons. ... The Mazda RX-8 is a sports car manufactured by Mazda Motor Corporation. ... The Porsche Carrera GT was a supercar manufactured by Porsche in Germany. ... The Ferrari F50 was a high-performance supercar made by Ferrari. ... The Chevrolet Corvette is a sports car that has been manufactured by Chevrolet since 1953. ... The Mercedes-Benz CLK-Class is a class of mid-size luxury rear-wheel drive coupés and convertibles. ... For an outline of all the Chevrolet Corvette generations see Main article: Chevrolet Corvette The Chevrolet Corvette C6 is the sixth and current generation of Chevrolet Corvettes built and marketed by Chevrolet. ... The BMW M5 is the high-performance version of the BMW 5-Series automobile made by BMW M GmbH. M5 versions of the E28, E34, E39 and E60 5-Series have been made. ... The BMW M6 is a high-performance version of the 6-Series automobile, designed by the motorsport division of the German manufacturer. ... Wikipedia does not have an article with this exact name. ... The BMW M5 is the high-performance version of the BMW 5-Series automobile made by BMW M GmbH. M5 versions of the E28, E34, E39 and E60 5-Series have been made. ... A naturally-aspirated engine or normally-aspirated engine (NA - aspiration meaning breathing) refers to an internal combustion engine (normally petrol or diesel powered) that is neither turbocharged nor supercharged. ...

Engine name Capacity Geometry Type Car Engine weight Power RPM power Torque RPM torque Power/Weight Reference
(liters) (application) (lb) (HP) (rpm) (lbf·ft) (rpm) (hp/lb)
BMW P84/5 3.0 V10 DOHC 2005 Williams FW27 F1 203 925 19,000 NA NA 4.56 [1]
Ferrari Tipo 052 3.0 V10 DOHC 2003 Ferrari F2003-GA F1 203 920 19,500 NA NA 4.53 [2]
Powertec RPB V8 2.8 V8 DOHC Radical SR9 194 450 NA 250 NA 2.32 [3]
Motopower RST-V8 2.0 V8 DOHC Various 163 340 10,250 190 7,000- 7,800 2.09 [4]
Powertec RPA V8 2.6 V8 DOHC Radical SR8 194 380 NA 215 NA 1.96 [5]

For other uses, see BMW (disambiguation). ... The Williams FW27 was the Formula One car which the Williams team used during the 2005 season. ... “F1” redirects here. ... Ferrari Enzo. ... The Ferrari F2003-GA was designed by Rory Byrne and Ross Brawn for the 2003 F1 season. ... “F1” redirects here. ... Wikipedia does not have an article with this exact name. ... Powertec RPA is the name of a V8 engine developed by Radical Motorsport in Peterborough England. ... Wikipedia does not have an article with this exact name. ...

See also

A traditional reciprocating internal combustion engine uses valves to to control air and fuel flow into and out of the cylinders, facilitating combustion. ... A cylinder head sliced in half shows two overhead camshafts—one above each of the two valves. ... It has been suggested that this article or section be merged with pushrod engine. ...

External links

  • Pushrod (OHV), SOHC and DOHC engine animated diagrams
  • LS7 torque and power by rpm chart
  • Ferrari Enzo: The Engine

  Results from FactBites:
 
Buick - Wikipedia, the free encyclopedia (1954 words)
Buick originated as an independent motor car manufacturer, the Buick Motor Company, incorporated on May 19, 1903 by the Scottish-American David Dunbar Buick (who invented the overhead valve engine on which the company's success was based) in Flint, Michigan.
In 1904 the struggling company was taken over by James Whiting, who brought in William C. Durant to manage his new acquisition.
The Buick V8 engine, nicknamed the "nailhead", became popular with hot-rodders in the 1950s and 1960s, because the vertical attachment of the valve covers, in contrast to the angled attachment of other V-8 engines, enabled the engine to fit into smaller spaces while maintaining easy access for maintenance.
  More results at FactBites »

 
 

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