It has been suggested that this article or section be merged with Cam-in-block. (Discuss)

A 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. Wikipedia does not have an article with this exact name. ... It has been suggested that this article or section be merged with pushrod engine. ... Components of a typical, four stroke cycle, DOHC piston engine. ... Double overhead cams control the opening and closing of a cylinders valves The camshaft is an apparatus used in piston engines to operate poppet valves. ... The cylinder 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, pistons, and flywheel Continental engine marine crankshafts, 1942 For the comic strip about an old, curmudgeonly bus driver, see Crankshaft (comic strip). ... 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 in which the pistons are aligned so that, if viewed along the line of the crankshaft, they appear to be in a V. Usually, two opposing pistons share one crank on the crankshaft. ... 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. ...

Pushrod engines are perceived to be "old fashioned" by the modern automotive press, the cause is historical: While both layouts are over 100 years old, the I-head engine came first. OHC engines were developed as more expensive high-performance engines and have largely replaced the pushrod design in countries where cars are taxed based on engine displacement. 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. Currently General Motors is the world's largest pushrod engine producer with engines such as the 3800 Series III Supercharged V6 (260 hp, 280 lb/ft torque), LS7 Corvette 7.0L V8 Engine (505 hp, 475 lb/ft torque) and LS4 5.3L DOD V8 (303 hp, 323 ft·lbf torque). Currently few pushrod type engines remain in production, a result of the fact that it has become difficult to achieve competitive engine performance with the configuration. Displacement, One complete cycle of a four cylinder, four stroke engine. ... The final Oldsmobile Logo, introduced in 1997 as an update of the Rocket theme used in various forms since 1948. ... The 1967 Toronados 425 V8, the first front-wheel drive V8 application. ... General Motors Corporation, also known as GM, is the worlds largest automaker and has been since 1931. ... The Buick V6 engine family, sometimes called the Fireball, 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 LS is Generation III and Generation IV, the latest evolution of General Motors line of small-block V8 engines. ... French steam corvette Dupleix (1856-1887) Canadian corvettes on antisubmarine convoy escort duty during World War II. A corvette is a small, maneuverable, lightly armed warship, smaller than a frigate but larger than a coastal patrol craft. ... 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. ...

Limitations

Three specific problems remain with pushrod engines:

• Limited engine speeds or rpm - Pushrod engines have more reciprocating mass, suffer more easily from valve "float", and exhibit a tendency for the pushrods themselves to flex or snap at high engine speeds. Therefore a pushrod engine cannot revolve ("rev") at engine speeds as high as an OHC design. Modern pushrod engines generally rev to 6,000 rpm: compare this to modern OHC engines that can easily rev from 7,000 rpm in average engines to near 20,000 rpm in Formula One racing engines. High-rev pushrod engines can and have also been developed — in 1969, Chevrolet offered a Camaro Z28 with a pushrod V8 that revved to 8,000 rpm. Volvo B18 and B20 engines can rev to more than 7000 rpm. The 2006 Chevrolet Corvette features a 7.0 L engine capable of revving to 7000 rpm. Custom manufactured or modified engines that utilize oversquare piston travel, and lightweight valvetrains similar to those used in NASCAR racing can rev in excess of 10,000 rpm but gear ratio rules have reduced the rpm's to about 9500 rpm. The 500 cubic inch displacement engines of various dragster are even capable of reaching 10,500 rpm.

Because overall power is computed by multiplying torque by revolution speed (HP = (RPM x LB-FT) / 5252), an engine capable of revving higher will produce more power from the same amount of torque than one revving lower. A pushrod engine therefore needs to have a larger displacement to match the power output of an OHC engine. A good comparison would be the 3.9L GM 3900 Engine to the 3.0L Honda J-series V6. The smaller (in displacement) Honda Engine produces more power, while requiring less torque to do so. Revolutions per minute (abbreviated rpm, RPM, r/min, or min-1) is a unit of frequency, commonly used to measure rotational speed, in particular in the case of rotation around a fixed axis. ... Formula One - Wikipedia, the free encyclopedia /**/ @import /skins-1. ... Chevrolet (IPA: ʃɛv. ... 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. ... The Chevrolet Corvette is a sports car that has been manufactured by Chevrolet since 1953. ... The National Association for Stock Car Automobile Racing (NASCAR) is the largest sanctioning body of motorsports in the United States. ...

• Difficulty in using crossflow cylinder heads in straight engine configurations - A few straight pushrod engines have been manufactured with crossflow heads, such as the six cylinder Humber Super Snipe. These engines combined much of the performance of the overhead camshaft with the ease of service of the pushrod, but were more expensive to manufacture than either competing design.

• Limited design flexibility - The biggest benefit of an OHC design is the use of multiple intake and exhaust valves and variable valve timing. Most modern pushrod engines have two valves per cylinder, while many OHC engines use 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. For the 2006 model year, General Motors introduced the Vortec 6200. This is the first mass-produced pushrod engine to feature variable valve timing. The system adjusts both intake and exhaust timing between two settings. There is even a company called Arao Engineering that has developed and patented a 32-valve aluminum cylinder heads for various pushrod engines like the small/big block Chevrolet engines and Ford small/big block engines.

A crossflow cylinder head is a cylinder head that features the intake and exhaust ports on opposite sides. ... 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. ... The Humber Super Snipe was a luxury car produced by Humber. ... 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. ... For other uses, see Cummins (disambiguation). ... 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. ... 2006 (MMVI) is a common year starting on Sunday of the Gregorian calendar. ... The model year of a product is a number used to describe approximately when a product was produced. ... General Motors Corporation, also known as GM, is the worlds largest automaker and has been since 1931. ... Vortec is a trademarked name for a line of piston engines for General Motors trucks. ...

Advantages

In contrast, pushrod engines have two specific advantages:

• Smaller overall packaging - Because of the camshaft's location inside the engine block, pushrods are generally 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 and 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.

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 or section does not cite its 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. ... Double overhead cams control the opening and closing of a cylinders valves The camshaft is an apparatus used in piston engines to operate poppet valves. ... Double overhead cams control the opening and closing of a cylinders valves The camshaft is an apparatus used in piston engines to operate poppet valves. ... 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. ...

1994 Mercedes 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 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, as Mercedes-Benz knew it would when deciding a victory at Indy was worth it. 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. ... 1994 (MCMXCIV) was a common year starting on Saturday of the Gregorian calendar, and was designated as the International Year of the Family and the International Year of the Sport and the Olympic Ideal by United Nations. ... Air foil bearing-supported turbocharger cutaway A turbocharger is an exhaust gas-driven compressor used to increase the power output of an internal-combustion engine by compressing air that is entering the engine thus increasing the amount of available oxygen. ... Air foil bearing-supported turbocharger cutaway A turbocharger is an exhaust gas-driven compressor used to increase the power output of an internal-combustion engine by compressing air that is entering the engine thus increasing the amount of available oxygen. ...

GM LS7 - an exceptional pushrod engine

General Motor's LS7 is a pushrod engine that deserves to be mentioned. Although comparing engines is not an exact science, let's just list some values illustrating the ever important power/weight ratio: The LS is Generation III and Generation IV, the latest evolution of General Motors line of small-block V8 engines. ...

The Porsche Carrera GT is a supercar, manufactured by Porsche of Germany. ... The Ferrari F50 is 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. ... 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. ... BMW M6 The BMW M6 is a high-performance version of the BMW 6-Series automobile, designed by BMW Motorsport. ... The Chevrolet Corvette C6 is a sports car that has not changed as much as the previous generation Corvette did. ... 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. ...

External links

• Pushrod (OHV), SOHC and DOHC engine animated diagrams
• LS7 torque and power by rpm chart