Roadmaster Estate Wagon V8-350 5.7L (1993)
Spark Plug: Description and Operation
The spark plugs protrude into the combustion chambers and provide the spark that ignites the compressed air/fuel mixture. There are many different
types of spark plugs for the many different applications and each type has specific advantages for its applications. Different features include:
Typical Spark Plug Construction
1.
THREAD SIZE - The diameter and pitch of the threaded portion of the spark plug.
2.
REACH - The length of the threaded portion and how far the electrode protrudes into the combustion chamber.
3.
FLAT SEAT - Flat seat spark plugs have a flat area where the spark plug seats against the cylinder head. These plugs are used with a metal gasket
that often must be threaded onto new spark plugs before installation.
4.
TAPERED SEAT - Some spark plugs have a tapered area where the plug seats against a tapered recess in the cylinder head. No gasket is used with
tapered seat spark plugs and correct tightening torque is especially critical, particularly when installed in aluminum cylinder heads.
Spark Plug Heat Range Illustrated
5.
HEAT RANGE - The ability of the spark plug to cool its electrodes.
a.
Hot plugs have longer insulators around the center electrode and less cross-sectional area for heat to transfer from the electrode to the
cylinder head. Heat is conducted away from the center electrode more slowly and the electrode tip stays at a higher operating temperature.
b.
Cold plugs have shorter insulators around the center electrode and a larger cross-sectional area for heat to transfer to the cylinder head. Heat
is conducted away from the center electrode quickly and the electrode remains at a cooler operating temperature.
