How2Day: 7 Engine Specifications

Certain basic terms define engine data and specifications. Colin Anderson/Brand X Pictures/Getty Images
Every engine has its own statistics and specifications. Engines made by American and foreign manufacturers come in many designs and configurations. Yet most of them use terms that relate to engine types, size, power and other factors that set their engines apart from others. Some terms have become synonymous with all manufacturers and allow people to categorize engines at a glance by reading these common terms and statistics.

The most basic identifier for an engine is its configuration. V-8 engines contain two rows of four cylinders each, designed in an angled bank or "V" shape. V-6 engines have the same design but have two fewer cylinders than the V-8. Straight four-cylinder engines have four cylinders in a straight, vertical line, whereas straight six-cylinder engines have an additional two cylinders. A slant six-cylinder engine has a similar design to the V-8, but two additional cylinders. Straight-line and V-shaped configurations comprise most engines made today.

Cubic inches, or in some applications, cubic liters, represent the total displacement of all the cylinders inside an engine. From the bottom of the piston at its lowest stroke to the top of its stroke defines the area inside the cylinder measured in cubic inches. The more cubic inches, the higher the amount of displacement.

Horsepower means work accomplished over a period of time, and has a number designation prescribed to each engine; for example, 250 hp or 300 hp. Horsepower can relate to configuration and cubic-inch size. The larger the engine, the more horsepower. One horsepower tabulates to 33,000 lb.-ft per minute. If a person were to lift 33,000 lbs. to a height of 1 foot for a duration of a minute, that person would be working at 1 horsepower, or expending 1 horsepower-minute of energy.

Torque, measured in foot-pounds, can best be defined as the initial pulling power from a static position or when the engine has to accelerate. Torque gets the engine moving, while horsepower keeps the engine moving. The torque or twisting force of all the rotational engine parts combines to set the engine in motion, sometimes quickly and sometimes slowly. The speed of the torque defines what the horsepower is, since the two figures work hand in hand. High-torque engines (with higher foot-pound numbers) can accelerate faster and haul heavier loads.

Bore measurement relates to the side-to-side (cross section) diameter of an individual piston cylinder, usually expressed in standard inches and sometimes in metric. When bore combines with stroke, the total fluid area of the piston displacement (cubic inches) can be tabulated. The larger the bore, the larger the piston.

When the top of the engine piston reaches the top of its combustion stroke (zero degrees) and then travels to the bottom (180 degrees) it has performed a stroke, measured in inches. Stroke measures the length of piston travel inside the cylinder. Some engines, called "strokers," have unusually long travel distances, which can be seen on high-performance engines in muscle cars.

The term "stock" describes an engine that has come from the factory with no modifications or high-performance options. The specifications have been fixed, regulated to strict tolerances. Replacement parts for such engines must be exact duplicates of the original parts. High-performance engines have optional parts and components that boost horsepower, torque and speed. Fuel injection, tuned exhaust, high-dome manifolds, a super- or turbo-charger, special needle bearings and the extensive use of aluminum throughout its design denote a high-performance engine that has been built to exceed stock or manufacturer's specifications.

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