Opel Corsa B 1993–2000 Service and Repair Manual: Valve clearances - adjustment

1. This adjustment should be carried out with the engine at its normal operating temperature. If it is being done after overhaul when the engine is cold, repeat the adjustment after the car has been driven a few kilometres when the engine will then be hot.

2. Begin by removing the air cleaner.

3. Mark the spark plug leads to ensure correct refitting and then pull them off the spark plugs.

4. Disconnect the engine breather hoses at the rocker cover (see illustration).

Removing the breather hose from the rocker cover

5. Undo the four bolts securing the rocker cover to the cylinder head and lift off the shaped spreader washers.

6. Withdraw the rocker cover from the cylinder head. If it is stuck give it a tap with the palm of your hand to free it.

7. Turn the engine by means of the crankshaft pulley bolt, or by engaging top gear and pulling the car forward, until No 1 piston is approaching TDC on the firing stroke. This can be checked by removing No 1 spark plug and feeling for compression with your fingers as the engine is turned, or by removing the distributor cap and checking the position of the rotor arm which should be pointing to the No 1 spark plug lead segment in the cap. The ignition timing marks on the pulley and timing cover must be aligned (see illustration).

Ignition timing marks (arrowed) in alignment

8. With the engine in this position the following valves can be adjusted - counting from the timing cover end of the engine.

1 - exhaust
2 - inlet
3 - inlet
5 - exhaust

9. Now turn the engine crankshaft through one complete revolution and adjust the following remaining valves:

4 - exhaust
6 - inlet
7 - inlet
8 - exhaust

10. As each clearance is being checked, slide a feeler blade of the appropriate size, as given in the Specifications, between the end of the valve stem and the rocker arm (see illustration). Adjust the clearance by turning the rocker arm retaining nut using a socket or ring spanner until the blade is a stiff sliding fit.

Checking a valve clearance

11. It is also possible to check and adjust the clearances with the engine running. This is done in the same way, but each valve is checked in turn. It will of course be necessary to refit the plug leads and No 1 spark plug if this method is adopted. To reduce oil splash place a piece of cardboard, suitably cut to shape, between the pushrod side of the rocker arms and the edge of the cylinder head.

12. After adjustment remove all traces of old gasket from the cylinder head mating face and renew the rocker cover gasket if it is cracked or perished.

13. Refit the rocker cover and secure with the retaining bolts and shaped spreader washers.

14. Refit the spark plug and plug leads, reconnect the engine breather hoses and refit the air cleaner.