CYLINDER HEAD DISTORTION
Clean the surface of the cylinder head. Use a reliable straightedge and feeler gauge to check the flatness of cylinder head surface.
Check along six positions as shown.
If beyond the specified limit, resurface or replace it. The limit for cylinder head resurfacing is determined by the cylinder block resurfacing.
After resurfacing cylinder head, check that camshaft rotates freely by hand. If resistance is felt, cylinder head must be replaced.
Nominal cylinder head height : 126.3 - 126.5 mm (4.972 - 4.980 in)
VALVE GUIDE CLEARANCE
Measure valve deflection as shown. (Valve and valve guide mostly wear in this direction.)
If it exceeds the limit, check valve to valve guide clearance.
If it exceeds the limit, replace valve or valve guide.
VALVE GUIDE REPLACEMENT
When valve guide is removed, replace with oversized [0.2 mm (0.008 in) ] valve guide.
To remove valve guide, heat cylinder head to 110° to 130°C (230° to 266°F) by soaking in heated oil.
Drive out the valve guide with a press [under a 20 kN (2.2 US ton) pressure] or hammer and suitable tool.
Ream cylinder head valve guide hole.
Valve guide hole diameter (for service parts), intake and exhaust : 10.175 - 10.196 mm (0.4006 - 0.4014 in)
Heat cylinder head to 110° to 130°C (230° to 266°F) by soaking in heated oil and press new valve guide from camshaft side into the cylinder head to the dimensions as shown.
Using a valve guide reamer, apply a reamer finish to the valve guide.
Intake and exhaust finished size : 6.000 - 6.018 mm (0.2362 - 0.2369 in)
VALVE SEAT CONTACT
After confirming that the dimensions of valve guides and valves are within specifications, perform this procedure.
Apply prussian blue onto contacting surface of valve seat to check the condition of the valve contact on the surface.
Check if the contact area band is continuous all around the circumference.
If not, grind to adjust valve fitting and check again. If the contacting surface still has N.G conditions even after the re-check, replace valve seat.
VALVE SEAT REPLACEMENT
Bore out old seat until it collapses. Boring should not continue beyond the bottom face of the seat recess in cylinder head. Set the machine depth stop to ensure this.
Ream cylinder head recess for service valve seat.
Be sure to ream in circles concentric to the valve guide center. This will enable valve seat to fit correctly.
Heat cylinder head to 110° to 130°C (230° to 266°F) by soaking in heated oil.
Press fit valve seat until it seats on the bottom.
After cutting, lap valve seat with abrasive compound.
Check valve seating condition.
Use a depth gauge to measure the distance between the mounting surface of the cylinder head spring seat and the valve stem end. If the distance is shorter than specified, repeat step 5 to adjust it. If it is longer, replace the valve seat with a new one.
VALVE SPRING SQUARENESS
Set try square along the side of valve spring and rotate the spring.
Measure the maximum clearance between the top face of spring and try square.
Out-of-square limit : Less than 2.0 mm (0.079 in)
VALVE SPRING DIMENSIONS AND VALVE SPRING PRESSURE LOAD
Check valve spring pressure at specified spring height.
If it is not within specifications, replace the spring.
