1 2 3 A torque wrench is required for the professional installation of a spark plug. Even for professionals the estimation of the tightening torque is nearly impossible. That is because a torque can be calculated from two sizes which are multiplied by one another: the force which is applied to the respective centre of rotation and the length of the handle. Most spark plug failures can be traced back to an incorrect tightening torque. If it is set too low, there is a risk of compression losses and overheating. A break of the insulator or middle electrode as a result of vibrations is also feasible. If the tightening torque is set too high, the spark plug can snap off. The casing can also expand or warp. Heat dissipation zones are disrupted, overheating and melting of the electrodes or even engine damage can occur. Seat type Spark plug tightening torques Cylinder head material Thread diameter fl at conical Cast iron Aluminium The required tightening torque depends on seat type, thread diameter and cylinder head material. Please take care of the tightening torques or angles, whenever these are printed on the packaging material! or or ALSO AS VIDEO IMPORTANT TIPS FOR THE INSTALLATION OF SPARK PLUGS 2 1 3 2 1 3 12 mm 15-25 Nm 15-20 Nm 14 mm 25-35 Nm 25-30 Nm 18 mm 35-45 Nm 35-40 Nm 10 mm ½ turn: 180° ½ – 2/3 turn: 180°–240° 1/16 turn: 22.5° 10-15 Nm 10-12 Nm 12 /14 mm 15-25 Nm 10-20 Nm 18 mm 20-30 Nm 20-30 Nm Cast iron head Angle of rotation, regardless of the cylinder head material Aluminium head Thread Ø Seat type Seat type 12 mm 14 mm 18 mm 10 mm 14 mm 18 mm Thread Ø Spark plug with a flat seat (with seal) Spark plug with a conical seat Spark plug with a flat seat (with seal) Spark plug with a conical seat The respective angle of rotation can be found on the spark plug packaging. (Exception: racing plugs – only torque method) Alternative: Angle of rotation details Niterra Co., Ltd. AICHI JAPAN Niterra Co., Ltd. AICHI JAPAN 28
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