Capri Definitions

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Adding an simple connection between the pipes can boost power in a certain rpm range. Most header primaries are tuned to operate on the second set of pressure waves, to tune the crossover to the same rpm range it will need to operate off the 1st set of waves. If your primary tube ends 30 inches. From the back of the valve and is using the second set of pressure waves, putting the crossover 60 inches from the valves will help power at the same rpm range using the 1st set of pressure waves. In order to be effective, the crossover should be at least 90% of the diameter of the pipes.


A half-shaft is an articulating, rotating shaft used in independent suspension systems to transmit power from a differential to a wheel. The term is also used to describe a non-articulating axle shaft.

    Hand Crank

A crank handle for manually starting internal combustion engines. Used till about 1930. Now obsolete.


A general term covering all the aspects of a car's behavior that are related to its directional control.

    Hauling Capacity

The maximum amount of weight, including driver, passengers, options or accessories, that can be carried in the truck's bed and cabin, and tongue weight if towing. Exceeding a vehicle's payload capacity can negatively affect steering and damage the suspension.

    Heavy-Duty Vehicle

Vehicle (truck) weighing from 26,001 to 33,001 lbs. Also included off-highway trucks.


A performance-oriented technique of down-shifting while braking that requires the driver to use all three pedals of a manual-transmission car simultaneously. To perform a heel-and-toe downshift, the driver brakes with the toe of his right foot and: while continuing to brake: uses the heel or the side of the same foot to blip the throttle and raise engine rpm as he downshifts. The left foot operates the clutch pedal in the normal fashion. The sequence is as follows: brake with the right toe; depress the clutch with the left foot; shift to neutral; while continuing to brake, blip the throttle with the side or the heel of the right foot to raise rpm; shift to a lower gear; let the clutch out; release the brakes. The technique is difficult to master, but after practice it can be performed in less than a second. This process is best for smooth power flow and long transmission life.

    Heim Joint

An extremely rigid articulating joint, commonly known as a ""spherical rod-end,"" used in any precision linkage. Heim joints are often used in the suspension links of race cars because they locate wheels very precisely.

    Helical Gear

A type of gear in which the teeth are cut at a slanting angle to the gear's circumference. A helical design produces an even, constant tooth loading in a gearset, thereby reducing noise.

    Hemispherical (Hemi)

A term used to describe any engine that has hemispherical combustion chambers in its cylinder heads. Hemi engines (most notably the 426ci Dodge V8) offer extremely good breathing characteristics and usually generate lots of power.


The removable or lift-up part of an auto body that covers the engine and allows access to it. (Bonnet in U.K.)


The common unit of measurement of an engine's power. One horsepower equals 550 foot-pounds per second, the power needed to lift 550 pounds one foot off the ground in one second: or one pound 550 feet up in the same time.

    Hotchkiss Suspension

A live-axle rear suspension in which leaf springs handle both the axle's springing and its location.


A production auto that has been modified by the owner for outstanding speed and acceleration through extensive changes to the engine, chassis, and body.


A mechanical operation based on incompressibility of liquids, generally oil and sometimes water, and their ability to offer resistance when being forced into a small cylinder or through an orifice, thereby transmitting an increase in applied force. Hydraulic brakes and clutches use this principle.

    Hydraulic Lifter

A valve lifter that, using simple valving and the engine's oil pressure, can adjust its length slightly: thereby maintaining zero clearance in the valvetrain. Hydraulic lifters reduce valvetrain noise and are maintenance-free.

    Hydraulic Valve Lifter

Valve lifter using hydraulic oil pressure to operate and capable of maintaining zero clearance between metal parts. Thus, valve noise and wear are considerably reduced as are the periodic valve adjustments.

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