Installation Manual

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Installation Instructions - Spark Plugs

1. Installing Spark Plugs

Torque is one of the most critical aspects of spark plug installation. Torque directly affects the

spark plugs' ability to transfer heat out of the combustion chamber. A spark plug that is

under-torqued will not be fully seated on the cylinder head, hence heat transfer will be slowed.

This will tend to elevate combustion chamber temperatures to unsafe levels, and pre-ignition

and detonation will usually follow. Serious engine damage is not far behind.

An over-torqued spark plug can suffer from severe stress to the Metal Shell which in turn can

distort the spark plug's inner gas seals or even cause a hairline fracture to the spark plug's

insulator...in either case, heat transfer can again be slowed and the above mentioned

conditions can occur.

The spark plug holes must always be cleaned prior to installation, otherwise you may be

torquing against dirt or debris and the spark plug may actually end up under-torqued, even

though your torque wrench says otherwise. Of course, you should only install spark plugs in a

cool engine, because metal expands when it's hot and installation may prove difficult. Proper

torque specs for both aluminum and cast iron cylinder heads are listed below.

2. Installing Spark Plugs - Lawn & Garden Equipment

* Confirm that the thread reach of the spark plug is the right one for your engine.

* Remove the dirt at the gasket seal of the cylinder head.

* Tighten the spark plug finger tight until the gasket reaches the cylinder head, then tighten

about 1/2-2/3 turn more with a spark plug wrench. (Taper seat: About 1/16 turn more).

3. Gapping

Since the gap size has a direct affect on the spark plug's tip temperature and on the voltage

necessary to ionize (light) the air/fuel mixture, careful attention is required. While it is a

popular misconception that plugs are pre-gapped from the factory, the fact remains that the

Summary of content (4 pages)

PAGE 1
Installation Instructions - Spark Plugs 1. Installing Spark Plugs Torque is one of the most critical aspects of spark plug installation. Torque directly affects the spark plugs' ability to transfer heat out of the combustion chamber. A spark plug that is under-torqued will not be fully seated on the cylinder head, hence heat transfer will be slowed. This will tend to elevate combustion chamber temperatures to unsafe levels, and pre-ignition and detonation will usually follow.
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gap must be adjusted for the vehicle that the spark plug is intended for. Those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap settings (to ensure ignitability in these denser air/fuel mixtures). As a rule, the more power you are making, the smaller the gap you will need. A spark plug's voltage requirement is directly proportionate to the gap size. The larger the gap, the more voltage is needed to bridge the gap.
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kits), and failure to address ALL of these areas will virtually guarantee engine damage. An engine that has poor oil control can sometimes mask the symptom temporarily by running a slightly hotter spark plug. While this is a "Band-Aid" approach, it is one of the only examples of when and why one would select a hotter spark plug. 6. Using "Racing" Spark Plugs Be cautious! In reality, most "racing" spark plugs are just colder heat ranges of the street versions of the spark plug.
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They store voltage, or accumulate it, until a point at which a trigger signal allows release of this more powerful spark. Companies like Mallory, MSD, Crane and Accel, to name a few, offer such systems. They affect spark plugs in that they allow the gaps to be opened up to take advantage of the increased capacity. The theory is that the larger and the more intense the spark you are able to present to the air/fuel mixture, the more likely you will be to burn more fuel, and hence the more power you will make.