Engine Glossary (G-I)

[ZfrkS62]

[size=18]G

galling wear caused by metal to metal friction due to inadequate lubrication. Metal is transferred from one surface to another.

gasohol mixture of gasoline and alcohol

gross horsepower power avialible with only the water pump and alternator using power

ground spark plug electrode The metal prong at the end of the threaded piece that can be bent towards or away from the electrode to ensure proper gap

[size=18]H

headers another term for exhaust manifolds, more commonly referred to in aftermarket situations, but can be used to described tuned headers on a stock performance engine.

heat range indication of how quickly heat can travel away from a spark plug's center electrode to the cooling system water jackets.

hemispherical combustion chamber a nonturbulent combustion chamberdesign shaped like a half globe

horsepower measurement of an engine's capability to do work

hot soak when the engine is shut off, particularly on hot days, and gasoline boils out of the float bowl onto the engine. This is also the term to describe what happens when an engine is shut off and sits in the latent heat being dissapated from the engine. Because there is no airflow, under hood temps rise substantially.

hydrolock when a cylinder is holding liquid either from a blown head gasket or leaking fuel injector, and comes up, the liquid reaches the combustion chamber, it cannot be compressed and stops rotation of the engine.

[size=18]I

I-head valve placement above the piston. This is the configuration in modern engines

I.D. Inside Diameter

IAC Idle Air Control motor. A stepper motor that controls the amount of air that reaches the engine while at idle. It is controlled by the engine computer

ignition system creates and distributes a timed spark to the cylinder

ignition timing The point of piston travel measured in degrees Before Top Dead Center in which the spark is delivered to the cylinder during the compression stroke

indicated horsepower The amount of pressure made in the combustion chambers

induction hardened valve seat integral valve seats that are harder than the surrounding area of the cylinder head

inert gas a gas which does not burn and takes up space in the combustion chamber

initial timing see base timing. the timing of the ignition system before the computer starts making changes

intake manifold vaccum pressure inside the intake manifold while the engine is running

integral seats and guides valve seats and guides that are made into the cylinder head and can not be replaced

intercooler also called an charge cooler or aftercharge cooler, it is a sophisticated air cooler for turbos and superchargers

interference angle the difference in angles between the valve seat and valve that results in increased pressure between the valve and seat, aidding in sealing.

internal balancing the act of balancing a crankshaft by drilling holes in the counterweights

ISC motor Idle Speed Control motor. same function as the IAC but opens the throttle plates instead of actuating a stepper motor