Description

HT Ignition Lead – No.4 Cylinder – high-tension ignition lead from the ignition coil and HT lead assembly, carrying the secondary ignition output to the spark plug at No.4 cylinder of the 4.0L and 4.6L Rover V8 petrol engine.

Leads in a V8 set are made to individual lengths matched to the routing of each cylinder position, so this lead is specific to No.4 and is not interchangeable with the leads for the other cylinders. Both ends carry insulating boots: one seals over the spark plug insulator, the other over its matching high-tension terminal.

HT leads are a wearing item. Insulation hardens and cracks with repeated heat cycling and conductor resistance rises with age, which typically shows up as a misfire under load, rough idle, or poor starting in damp weather. A degraded lead can also track to earth or to a neighbouring lead, so all eight are normally renewed together to keep secondary resistance consistent across the engine.