Spark Plug Thread, Recondition
Remove cylinder head - see operation "Cylinder Head, Remove and Install".
Using a commercially available spark plug insert tap, ream and recut thread in one operation (observe manufacturer's instructions!)
Screw thread insert onto spark plug - dimension I = 17 mm/0.67 in. Screw in spark plug - 25 Nm / 18 lbf. ft.
The chemically treated surface of the thread insert creates a firm connection between the thread insert and the cylinder head when the engine is run warm.
Install cylinder head - see operation "Cylinder Head, Remove and Install".