Spark Plug for the ignition system of 2.5L 4-cylinder and 3.5L V8 petrol engines. The plug seals the combustion chamber and carries high-tension voltage from the ignition lead down the centre electrode to the gap, where the spark ignites the compressed charge. It uses a 14 mm thread with a 19 mm reach and a gasket seat, sealing against a washer rather than a tapered face. The insulator nose is of the projected type, placing the electrode gap further into the combustion chamber. This exposes the tip to the incoming charge for better ignition and improved cold running, while the additional cooling from that same incoming charge helps keep the firing end clean at light load without overheating at high load. Electrode gap should be checked against the engine specification before fitting, and the plug tightened to the specified torque on a clean seat.
