This adjustment is required only on the six-cylinder; it should be done at every tune-up or whenever there is excessive noise from the valve mechanism.
Do not set the valve lash closer than specified in an attempt to quiet the valve mechanism. This will result in burned valves.
The valves can be adjusted with the engine running, but the amateur will have better luck with the following procedure.
- The engine must be at normal operating temperature. Mark the crankshaft pulley into three equal 120° segments, starting at the timing mark.
- Remove the valve (rocker) cover and the distributor cap.
- Set the engine at TDC on the No. 1 cylinder by aligning the mark on the crankshaft pulley with the 0° mark on the timing cover pointer. The distributor rotor should point at the position of the No. 1 spark plug wire in the distributor cap. Both rocker arms on the No. 1 cylinder should be free to move slightly. If all this isn't the case, you have No. 6 cylinder at TDC and will have to turn the engine 360° in the normal direction of rotation.
- The cylinders are numbered from front to rear. The intake and exhaust valves are in the following sequence, starting at the front: E-I, E-I, E-I, I-E, I-E, I-E. Note that intake and exhaust valves have different settings.
- The lash is measured between the rocker arm and the end of the valve.
- To check the lash, insert the correct size feeler gauge between the rocker arm and the valve. Press down lightly on the other end of the rocker arm. If the gauge cannot be inserted, loosen the self-locking adjustment nut on top of the rocker arm. Tighten the nut until the gauge can just be inserted and withdrawn without buckling.
- After both valves for the No. 1 cylinder are adjusted, turn the engine so that the pulley turns 120° in the normal direction of rotation (clockwise). The distributor rotor will turn 60°, since it turns at half engine speed.
- Check that the rocker arms are free and adjust the valves for the next cylinder in the firing order, 5. The firing order is 1-5-3-6-2-4.
- Turn the engine 120° to adjust each of the remaining cylinders in the firing order. When you are done the engine will have made two complete revolutions (720°) and the rotor one complete revolution (360°).
- Replace the rocker cover with a new gasket. Replace the distributor cap. Start the engine and check for leaks.