How do I install spark plugs correctly?

It is essential to tighten a spark plug to the specified turning angle or torque setting. First, screw in the plug finger tight until the gasket meets the cylinder head. Then seat the plug/gasket with a torque or turning angle wrench as specified in the chart below. This is very important, as excessive tightening of a spark plug can cause breakage of the metal shell and damage to the interior seals. At the same time, insufficient tightening can lead to overheating of the spark plug and potential detonation.

Spark Plug Type Thread Diameter Cast Iron Cylinder Head (lb-ft.) Aluminum Cylinder Head (lb-ft.)
Flat seat type (with gasket) 18 ø mm 25.3~32.5 25.3~32.5
Flat seat type (with gasket) 14 ø mm 18.0~25.3 18.0~21.6
Flat seat type (with gasket) 12 ø mm 10.8~18.0 10.8~14.5
Flat seat type (with gasket) 10 ø mm 7.2~10.8 7.2~8.7
Flat seat type (with gasket) 8 ø mm 5.8~7.2
Conical seat type (without gasket) 18 ø mm 14.5~21.6 14.5~21.6
Conical seat type (without gasket) 14 ø mm 10.8~18.0 7.2~14.5