The high tension cables conduct the high output voltage generated in the secondary ignition circuit when each ignition pulse occurs. They link the high tension terminal of the ignition coil, the distributor cap and spark plugs.
Because of the high voltage, the cables are large in diameter, and are made from thick-walled insulating material around a central conducting core. The heavy insulation prevents leakage occurring and also withstands the effects of high temperature, oil and moisture.
The core of the cable is made of carbon-impregnated linen or fiberglass. It has a specific ohmic resistance value.
A crimped terminal at each end provides for connection of the components.
With HEI ignition systems, the quality of the HT leads, in particular the casing, is of utmost importance. As the current is conducted down the leads a magnetic field around the lead can be induced. If the insulation around the cable is insufficient and the leads are crossed or closely coupled, then an induced voltage can be generated in the other wires. In some instances this could lead to premature firing of the spark plug when it is not in sequences.