2. Spark plugs must be replaced at the intervals specified in the section "Routine maintenance" at the beginning of this Guide. A thorough inspection of spark plugs can tell you a lot about the condition of your engine.
3. If the spark plug's heat cone is clean and white, without any dark deposits, this is a sign of a too-lean mixture or a spark plug that is too hot (a hot spark plug transfers heat from the electrode slowly, while a cold spark plug does so quickly).
4. If the top and heat cone of the spark plug are covered with a thick black coating, this is a sign of an overly rich mixture. If the spark plugs are covered with a black oily coating, this indicates that the engine is very worn and the mixture is most likely too rich.
5. If the heat cone is covered with a coating from light brown to gray-brown in color, this means that the mixture has the correct composition, and the engine is most likely in good condition.
6. The size of the spark gap is of great importance. If it is too big or too small, the spark plug's performance will be greatly reduced. For the correct spark gap value see. in the Specifications at the beginning of this chapter.
7. The spark gap size is adjusted by bending the side electrode. Do not attempt to bend the central electrode under any circumstances, as this may damage the insulator.
8. Recommended types of candles are indicated in Specifications. The spark plugs must have a conical body and be installed without washers. Since the head is made of light alloy, be careful not to overtighten the spark plugs. It is best to use a torque wrench with a long spark plug socket to tighten them. Check that the spark plug bodies and spark plug hole walls are clean. Check that the ignition wires are connected in the correct order (see B/Figure 4.5).
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9. Ignition wires do not require routine maintenance. It is enough to keep them clean and wipe them regularly. When removing spark plugs for servicing or replacement, disconnect the wires one at a time to avoid mixing them up. Before connecting the wires, clean their ends from traces of corrosion and thoroughly wipe the terminals under the wires on the distributor cap.
10. High tension wires slowly lose their performance over time, so it is recommended to replace them regardless of condition during normal engine maintenance. It's better not to throw away old wires, but to leave them in the car just in case.