Tappet Guides

CAUTION: The following procedure is not recommended owing to the difficulty of removing the old tappet guide and the risk of damage to the cylinder head; it should not be attempted unless comprehensive machine shop facilities are available. A replacement cylinder head should be considered as an alternative.

Tappet Guide:

1. Remove the old tappet guide (1) by boring out until the guide collapses Take great care not to damage the guide bore in the cylinder head.
2. Carefully measure the diameter of the tappet guide bore at room temperature 20°C (68°F).
3. Grind down the outside diameter of the replacement tappet guide to a dimension 0.089 mm (0.0035 in) larger than the tappet guide bore diameter measured above.
4. Grind the same amount from the 'lead-in' at the bottom of the tappet guide. The reduction in diameter from the adjacent diameter should be 0.089 to O.16 mm (0.0037 to 0.0062 in).
5. Heat the cylinder head in an oven for half an hour from cold at a temperature of 15O°C (300°F).
6. Fit the tappet guide (2), ensuring that the lip at the top of the guide beds evenly in the recess in the top of the cylinder head.
7. Allow the cylinder head to cool, then ream the tappet guide bore to the diameter of 34.925 mm + 0.018 mm - 0.000 mm (1.375 in + 0.007 in - 0.000 in).
8. It is essential that, when reamed, the tappet guide bore is concentric with the valve guide bore.