The spark plug wires should be checked at recommended intervals or whenever new spark plugs are installed, inspecting them one at a time to prevent mixing up the order, which is essential for proper engine operation. Disconnect the plug wire from the spark plug using a removal tool or by grabbing the rubber boot, twisting slightly, and pulling the wire free without pulling on the wire itself. Inspect inside the boot for corrosion, which appears as a white, crusty powder, while later models may use a conductive white grease that should not be mistaken for corrosion. Push the wire and boot back onto the spark plug, ensuring a tight fit; if it is not secure, carefully crimp the metal connector inside the wire boot with pliers. Clean the wire along its entire length with a clean rag, removing built-up dirt and grease while inspecting for burns, cracks, or other damage, bending the wires in several places to check if the conductive inside wire has hardened. Disconnect the wire at the distributor, again pulling and twisting only on the rubber boot, checking for corrosion and a tight fit as with the spark plug end; for HEI ignition systems, release the locking tabs on the circular retaining ring to check all wire boots simultaneously. Reinstall the wire boot or retaining ring onto the top of the distributor and check the remaining spark plug wires in the same manner, ensuring they are securely fastened at both the distributor and spark plug. A visual check can also be performed in a darkened garage by starting the engine and observing each plug wire for arcing or small sparks at damaged areas, taking care to avoid contact with moving engine parts. If replacement is necessary, purchase a new set specific to the engine model, as wire sets can be pre-cut to the proper size with rubber boots already installed, and for HEI ignition systems, replace each wire individually to prevent mix-ups in the firing sequence.