A metric engine is an American expression which refers to an

internal combustion An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combust ...

engine An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power ...

, often for automobiles, whose underlying

engineering Engineering is the use of scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad range of more speciali ...

design is based on a metric system of units, particularly SI. As American industry converted from traditional units to SI in the late 20th century, the

automotive industry The automotive industry comprises a wide range of companies and organizations involved in the design, development, manufacturing, marketing, and selling of motor vehicles. It is one of the world's largest industries by revenue (from 16 % such ...

responded by transitioning its auto and engine designs to be "metric" rather than "English".

Characteristics

A metric engine has one or more of the following characteristics:

Tools

* A metric engine may require metric

tool A tool is an object that can extend an individual's ability to modify features of the surrounding environment or help them accomplish a particular task. Although many animals use simple tools, only human beings, whose use of stone tools dates ba ...

s for repair, such as

wrench A wrench or spanner is a tool used to provide grip and mechanical advantage in applying torque to turn objects—usually rotary fasteners, such as nuts and bolts—or keep them from turning. In the UK, Ireland, Australia, and New Zeala ...

and

socket Socket may refer to: Mechanics * Socket wrench, a type of wrench that uses separate, removable sockets to fit different sizes of nuts and bolts * Socket head screw, a screw (or bolt) with a cylindrical head containing a socket into which the hexag ...

sets designed to fit metric fasteners.

Units

Displacement Displacement may refer to: Physical sciences Mathematics and Physics * Displacement (geometry), is the difference between the final and initial position of a point trajectory (for instance, the center of mass of a moving object). The actual path ...

of the engine's cylinders measured in

liters The litre (international spelling) or liter (American English spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3). ...

cubic centimeters A cubic centimetre (or cubic centimeter in US English) (SI unit symbol: cm3; non-SI abbreviations: cc and ccm) is a commonly used unit of volume that corresponds to the volume of a cube that measures 1 cm × 1 cm × 1 cm. One cu ...

(cm³). Previously, American engine displacement was most typically measured in cubic inches (in³). Many classic American automobiles had engines popularly known by the displacement of their engine, such as the "350" Chevrolet

Small-block The Chevrolet small-block engine is a series of gasoline-powered, V-8 automobile engines, produced by the Chevrolet division of General Motors between 1954 and 2003, using the same basic engine block. Referred to as a "small-block" for its size ...

, the Ford 302 and 427, or the Chrysler "426 Hemi". Beginning around the 1970s, most of the U.S. automakers began converting their engine designations from cubic inches to liters. Thus, in 1970, the V-8 engine in the

Cadillac Eldorado The Cadillac Eldorado is a luxury car manufactured and marketed by Cadillac from 1952 until 2002 over twelve generations. The Eldorado was at or near the top of the Cadillac line. The original 1953 Eldorado convertible and the Eldorado Brougham ...

grew to 500 cubic inches, but was badged "8.2 Liters" for the first time. Once this conversion was complete, engines worldwide were most commonly referred to by their displacement in liters. This conversion must have caused some

marketing Marketing is the process of exploring, creating, and delivering value to meet the needs of a target market in terms of goods and services; potentially including selection of a target audience; selection of certain attributes or themes to emph ...

dilemmas: Ford's "302 Windsor" engine, which displaced approximately 4942 cc, became badged "5.0" after metric conversion. Some usage of cubic inches continues in the 21st century, such as in traditional American-style

motorcycles A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle steered by a handlebar. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commuting, cruising ...

; and the occasional new-era

muscle car Muscle car is a description according to '' Merriam-Webster Dictionary'' that came to use in 1966 for "a group of American-made two-door sports coupes with powerful engines designed for high-performance driving." The '' Britannica Dictionary'' ...

, such as the 2004

Dodge Viper The Dodge Viper is a sports car that was manufactured by Dodge (by SRT for 2013 and 2014), a division of American car manufacturer FCA US LLC from 1992 until 2017, having taken a brief hiatus in 2007 and from 2010 to 2012. Production of the two- ...

, which boasted a 500 cubic inch (8,193 cc), 500 horsepower (373 kW) engine, or the Ford "427" concept car. In the case of such cars, the use of cubic inches, rather than the metric cubic centimeters, can be considered

vestigial Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...

Footnotes

* The terms SI and metric system are not strictly interchangeable; the common "metric system" refers to a system of units based on powers of 10, for example, the cgs system; while SI was originally based on the MKS system of units. However, such distinctions are not relevant in the typical engine repair facility. {{DEFAULTSORT:Metric Engine (American Expression) Automobile engines Metrication in the United States