Ignition leads, also known as spark plug wires, deliver high-voltage electricity from the ignition coil to the spark plugs, initiating combustion within the engine cylinders. These multi-strand copper core cables are insulated with silicone or PVC to prevent voltage leakage and withstand high temperatures. Internal resistance is tightly controlled to maximize spark energy and ensure consistent engine firing. Leads are routed from the distributor or coil pack, following engine geometry, and terminate with a conductive terminal securely fitted to each spark plug. Proper length and resistance values are critical for optimal engine performance and emissions control.