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Spark Plug Tips


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How Does Heat Range Affect A Plug?

A spark plug is made up of ceramics, steels and nickel alloys. These materials do not have the ability to produce energy or heat. When we talk about the heat range of a spark plug, we're referring to its ability to move heat away from its tip or core nose into the cooling system. A cold spark plug would have a cooler tip temperature than a hot one. With today's fuels, we know that anytime the tip of the ceramic core nose goes below 850 F, carbon will build up and the spark plug will foul. We also know that if the tip temperature of the plug exceeds 1550', the metals will begin to break down. At approximately 1700, the plug will glow and can become a source of pre-ignition within the combustion chamber. Armed with this information, it becomes clear that maximum performance can be achieved with a spark plug that has a temperature of greater than 850 at idle, but no more than 1550' under wide open throttle.

Installation Tips

Here are a couple of tips to help assure the success of changing spark plugs. The first is to remove spark plugs from aluminum cylinder heads only when the engine is cool. Since aluminum and steel expand and contract at different rates, removing spark plugs from an aluminum cylinder head while hot can actually cause thread and cylinder head damage. Before installing the spark plugs, make sure the threads are clean and in good condition. If in doubt, run a thread chaser through the plug opening in the cylinder head. Most plug manufacturers recommend that you do not use an anti-seize compound, since one has already been applied to the plugs at the factory. Next, install the spark plugs finger tight and, it using a taper seat spark plug, use a ratchet to rotate 1/16 of a turn. If using a gasket seat type spark plug, after installing finger tight, turn 1/4 to 5/8 of a turn. If this procedure is followed, spark plugs will not back out nor will they seize in the cylinder head.