If suitable measuring equipment is not available guide wear may be estimated by inserting a new valve until the end of the valve is flush with the end of the valve guide. Rock the valve to and fro in this position and measure the maximum movement of the head of the valve. The guides should be renewed when this movement exceeds mm.
To fit a new guide the head should again be heated, and ideally the guide should also be cooled in liquid nitrogen. Fit the guide using Special Tool No. 8 2 3 1. If this is not available take particular care that the method used does not drive the circlip into the aluminium alloy of the cylinder head.
Note: Take particular care in view of the extremes in temperature of the cylinder head and the new valve guide, which should not be handled with bare hands.
