Note: The valve clearances must be checked and adjusted only when the engine is cold.

1 The importance of having the valve clearances correctly adjusted cannot be overstressed, as they vitally affect the performance of the engine. If the clearances are too big, the engine will be noisy (characteristic rattling or tapping noises) and engine efficiency will be reduced, as the valves open too late and close too early. A more serious problem arises if the clearances are too small, however. If this is the case, the valves may not close fully when the engine is hot, resulting in serious damage to the engine (eg. burnt valve seats and/or cylinder head warping/cracking). The clearances are checked and adjusted as follows.

2 Disconnect the spark plug HT leads and remove the oil filler/crankcase ventilation cap from the rocker cover.

3 Remove the rocker cover and then turn the engine using a spanner on the crankshaft pulley nut until the valves on No 1 cylinder are rocking (ie inlet valve opening and exhaust valve closing).

4 The rocker arm clearances of both valves of No 4 cylinder can now be checked and, if necessary, adjusted. Remember that No 1 cylinder is at the flywheel/clutch end of the engine.

5 The feeler blade of the correct thickness is inserted between the valve stem and rocker arm. When the clearance is correctly set the feeler blade should be a smooth stiff sliding fit between the valve stem and rocker arm. The correct valve clearances are given in the Specifications at the start of this Chapter. The valve locations can be determined from the position of the manifolds. Note that engines manufactured from January 1987, with bi-metal rockers consisting of an aluminium arm and steel pad, have different valve clearances than earlier engines. Ensure that the correct figures are used according to engine type.

6 If the feeler blade is a tight or loose fit then the clearance must be adjusted. To do this, loosen the locknut of the adjustment stud and screw the adjuster stud in or out until the feeler blade can be felt to drag slightly when drawn from the gap.

7 Hold the adjuster firmly in this position and tighten the locknut. Recheck the gap on completion to ensure that it has not altered when locking the nut and stud (see illustration).

2.7 Adjusting the valve clearances

8 Check each valve clearance in turn in the following sequence remembering that the clearances for inlet and exhaust valves are different. The valves are numbered from the flywheel end of the engine.

Valves rocking Valves to adjust 1 In 2 Ex 7 In 8 Ex
5 In 6 Ex 3 In 4 Ex
7 In 8 Ex 1 In 2 Ex
3 In 4 Ex 5 In 6 Ex
9 Fit the rocker cover using a new gasket, then refit the spark plugs, HT leads and oil filler/crankcase ventilation cap.