Jaguar Cylinder head bolt

Jaguar: XJS 4.0 with AJ16 engine from engine no. B100136 (1994-96) • X300 (XJ) 3.2 and 4.0 from VIN...720125 to 812255 (1993-97)

Aston Martin: DB7 3.2 litre six cylinder models (1994-99)

It is now Jaguar Cars policy that the cylinder head bolts of AJ16 engines should be re-used twice in service, during repair operations involving removal of the cylinder head. To be able to identify the number of times a bolt has been reinstalled, it is mandatory that bolts are marked as detailed below.
Action: Before reusing a cylinder head bolt, clean the threads thoroughly. After reinstalling and fully tightening a used cylinder head bolt (except when a new bolt has been installed), mark the bolt head with ONE punch mark, using automatic center punch.
A second removal and reinstallation is permissible. A bolt showing one punch mark may be reinstalled, and marked with a second punch mark.
When removing a bolt already marked with two punch marks, it must be discarded.
Any bolt showing obvious signs of damage must be replaced.