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Ha
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Ho
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Halogen
lamp A high-output, white-light lamp used as a headlight. Also
known as halogen light.
Halfshaft
A rotating shaft that transmits power from the final drive unit to a
drive wheel, usually when referring to a live rear axle.
Hard
Pedal
1.
A loss in braking efficiency so that an excessive amount of pressure
is needed to actuate brakes.
2.
A condition whereby the load literally overrides the brakes.
Harmonic
Balancer A device designed to reduce torsion or twisting
vibration in the crankshaft. May be incorporated in the crankshaft
pulley. Also known as a vibration damper.
Head
1.
That part of an engine that covers the top of the cylinders
and pistons and
usually contains the combustion
chambers and valve
train.
2.
That part of a compressor that covers the valve plates and separates
the high side from the low side of an air-conditioning system.
Head
Gasket A gasket that is used to enhance sealing between a
cylinder head and an exhaust manifold or header.
Headers
A
header is a different type of manifold; it is made of separate
equal-length tubes.
Headlights
Headlights are mounted on the front of the car to light the road
ahead during night or foggy days. They have reflectors and special
lenses and are usually the sealed beam construction type, with the
filament, reflector and lens fused together into an airtight unit.
The most popular type of headlight is the halogen type, because it
provides bright illumination. The halogen bulb is filled with
pressurized gas (halogen) and can produce flying fragments if
shattered. Wear protective glasses for changing a halogen lamp and
always throw out the old one in the protective carton that comes with
the new one.
Heat
Exchanger The "heat exchanger" is a device that uses
exhaust heat to aid in fuel evaporation. It usually is built into the
intake manifold as an area where the hot exhaust gasses and fuel-air
mixture come close to each other.
Heater
Core The heater core is a smaller version of the radiator that
is used to keep your toes warm when it's cold outside. It is mounted
under the dashboard. Some of the hot coolant is routed through this
little radiator, by more hoses. A small electric fan is also mounted
there especially for the purpose of directing the heat inside the
car. The principle is exactly the same as the one used in the
radiator for your engine, except that the heat is released inside the
car instead of outside.
Helical
Gear
A gear in which the teeth are cut at an angle to the shaft. The
advantage is that there are usually two teeth meshing at all times,
making for smoother and quieter operation.
Hemi
Slang term for an engine with hemispherical combustion chambers
which allow for larger and less shrouded valves. Used in many sports
and racing cars.
Hemi-Head
A
hemispherically shaped combustion chamber at the top of the engine
cylinder. The hemispheric shape provides improved efficiency because
the forces of the explosion are directed to the piston by the curved
surface of the combustion chamber.
High-Performance
Tire A tire with serious traction capabilities, usually
for both straight-line acceleration and cornering performance. Many
high-performance tires feature a soft rubber tread compound, which
enhances traction but can shorten the tire's lifespan. Of course,
people who are in search of optimum traction usually are willing to
sacrifice a bit of tire longevity, as well as some performance in
rain and snow.
Hone
An abrasive tool for correcting small irregularities or differences
in diameter in an engine cylinder, brake cylinder, etc.
Hood
The removable or lift-up part of an auto body that covers the engine
and allows access to it.
The
car's hood consists of an inner and an outer panel. The inner panel
provides strength, while the outer panel is just a metal cover. The
underside of the hood is often covered with a sound-absorbing
material. Some high performance cars have 'hood scoops' which channel
outside air directly to the air filter, which gives improved
performance and efficiency. The hood release is a small lever, which
is usually mounted under the dash. It is connected to the hood latch
by a cable. The hood latch has a safety feature, which requires a
second latch to be released before the hood will open. This is to
prevent accidental opening while driving.
Horsepower
(hp.) The unit for measuring the power output of an engine. One
horsepower is defined as lifting 33,000 pounds one foot per minute.
Horn A
device for sounding an alarm. On some entry level vehicles, a single
horn makes a high pitch beep. On more expensive vehicles, the sound
is made with two or more horns. The sound is made by an electrical
charge which activates and deactivates a coil. The sound is then
magnified by the shape of the horn. Large truck horns make a very
loud noise because the sound is made by passing compressed air
through the sounding device. A Claxton horn makes a sound that
resembles the word "A-hoo-gah."
Hubcap
Often used as a synonym for wheelcover. In more literal terms, a
wheelcover covers the entire wheel, while a hubcap covers only the
center of the wheel, or the hub. “Dog-dish” hubcaps are
popular among enthusiasts who like a sleeper look, and they often
were found on police cars of the ’60s and ’70s.
Hydraulic
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 Assisted
Brakes See brake
booster.
Hydraulic Brakes
See brake booster.
Hydraulic Brake
Booster hydraulic pressure supplied by the power steering pump,
or a separate hydraulic pump, which is used to assist in applying the
brakes; used on cars and on some trucks
Hydraulic Assisted
Brakes Brakes operated by hydraulic pressure.
See brake booster.
Hydraulic Braking
System: Brakes operated by hydraulic pressure
Hydraulic
Tappet A tappet
that utilizes hydraulic pressure from the engine's lubrication system
to maintain zero clearance (constant contact with both camshaft
and valve stem). Automatically adjusts to variation in valve stem
length. Hydraulic tappets also reduce valve noise.
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.
Hydroplaning
A wet-weather phenomenon in which a vehicle's tires ride upon a thin
layer of water and lose contact with the road surface. Tires
typically are designed with grooves or water channels to prevent hydroplaning.
Hypoid
Gears A type of differential final drive using a spiral
bevel gear on the drive shaft, allowing it to be located below the
center of the ring gear on the axle. This makes possible a lower
floor in the car.
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