Valve Clearance Adjustment

PROCEDURE

Counting from the camshaft drive end: valves No. 1, 3, 6 and 8 are exhaust valves; valves No. 2, 4, 5 and 7 are intake valves. Clearances are adjusted with adjusting shims, which are available in thicknesses from 3 to 4.25 mm in 0.05 mm steps. The thickness is marked on one side of the shim. Clearances on a cold engine (coolant temperature 20 ± 5 °C) must be: intake valves 0.20 ± 0.05 mm; exhaust valves 0.40 ± 0.05 mm. Clearances on a warm engine (coolant temperature 35 °C and above) must be: intake valves 0.25 ± 0.05 mm; exhaust valves 0.45 ± 0.05 mm. Adjust the valve train clearances on a warm engine, with coolant temperature at 35 °C, after every 30,000 km. Clearances must also be adjusted after lapping and grinding the valves and valve seats, and after replacing the camshaft. In these cases, recheck the valve train clearances on a warm engine after 1,000 km. PROCEDURE 1. Remove the cylinder head cover. 2. Turn the crankshaft so that the camshaft lobes on the cylinder being checked face up. Measure the clearance between the cam lobe and the tappet with a feeler gauge and record the result. Measure the valve clearances on all other cylinders in the same way. The feeler gauge should slide between the cam and tappet with noticeable resistance. Adjustment sequence: cylinders 1, 3, 4 and 2. Turning the crankshaft will be easier if the spark plugs are removed. 3. If the clearance is not within specification, replace the adjusting shim. To do this, turn the crankshaft so that the piston in the cylinder being checked is not at TDC. Then, using a special tool, press down the tappet and depress it far enough to remove the adjusting shim. There are two cutouts on top of the tappet to make shim removal easier. After removing the shim, read the thickness marked on its reverse side. Compare the shim thickness with the measured clearance and calculate the thickness of the shim to be installed. Example: the clearance measured on an exhaust valve is 0.15 mm and the nominal clearance is 0.45 mm. The clearance is therefore 0.3 mm less than required.

The thickness of the adjusting shim removed from the tappet is 3.60 mm. Therefore, the thickness of the new adjusting shim must be 3.60 – 0.30 = 3.30 mm.

WARNING Do not rotate the crankshaft with the adjusting shim removed, as the camshaft may damage the tappet. 4. Install the new adjusting shims with the marking facing down, toward the tappet. 5. Install the cylinder head cover with a new gasket. If only the clearances were adjusted (without cylinder head repair, valve lapping, etc.), recheck the clearances after the parts have run in, at 5,000 km. If the adjusting shims are not worn or damaged, they can be reused when removed. Checking the condition of the hydraulic tappets (see subsection 2.2.1.6).