Valve Springs:

Valves should be ground into re-cut valve seats. To this, coat the valve seat with fine lapping compound and use a suction tool. Move the valve backwards and forwards, as demonstrated in Fig. 1.53. Ever so often lift the suction tool, move it forward by ¼ of a turn and continue grinding. Work the seat until an uninterrupted ring is visible around the face of the valve. After grinding-in, clean the cylinder head, and even more important the inside of the valve guide bores thoroughly. Any lapping paste inside the cylinder head will accelerate the wear of the new parts.

Fig. 1.53. — Grinding-in of a valve.

Use a pencil and mark across the valve seat closely spaced. Drop the valve into the respective valve guide and turn the valve by 90°, using the suction tool, applying slight pressure to the tool. Remove the valve and check if the pencil marks have been removed from the entire circumference. The gap created will indicate the width of the valve seat and can be measured with a ruler or caliper. Otherwise repeat the grinding-in until this is the case.

Valve Springs:

If the engine has a high mileage, always replace the valve springs as a set. To check a valve spring, place the old spring and a new spring end to end over a long bolt (with washer under bolt head) and fit a nut (again with a washer). Tighten the nut until the springs are under tension and measure the length of the two springs. If the old spring is shorter by more than 10%, replace the complete spring set. Check the free length of the valve springs (Fig. 1.54) and compare the values with the dimensions given in Section 1.4.0.0.

Fig. 1.54. — Measuring the free length of a valve.

Valve Guides:

Measure the inside diameter of the guides, as shown on the R.H. side in Fig. 1.51. As an inside micrometer is necessary for this operation, which is not always available, you can insert the valve into its guide and withdraw it until the valve head is approx. level with the cylinder head face. Rock the valve to and fro and check for play. Although no exact values are available, it can be assumed that the play should not exceed 1.0 - 1.2 mm (0.04 - 0.047 in.).

Valve guides are available with oversize outside diameter (see Section 1.4.0.0.) and the locating bores in the cylinder head must be bored out to take the new guides. This may be a job for the workshop. Drive out the guide with a suitable mandrel. The cylinder head should be heated in boiling water to facilitate the operation. Measure the protruding end of the guide (write it down) before driving the old guide out and drive in the new guide to obtain the same dimension.