Valve Spring
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 alone six Positions as shown.
Head surface distortion
Limit 0.1 mm (0.004 inch)
Standard Less than 0.03 mm (0.0012 inch)
If beyond the specified limit, resurface or replace it.
The limit for cylinder head resurfacing is determined by the cylinder block resurfacing.
Resurfacing Limit
Amount of cylinder head resurfacing is "A".
Amount of cylinder block resurfacing is "B".
The maximum limit A + B = 0.2 mm (0.008 inch)
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 inch)
VALVE GUIDE CLEARANCE
1. Measure valve deflection as shown. (Valve and valve guide mostly wear in this direction.)
Valve deflection limit (dial gauge reading)
Intake 0.24 mm (0.0094 inch)
Exhaust 0.28 mm (0.0110 inch)
2. If it exceeds the limit, check valve to valve guide clearance.
a. Measure valve stem diameter and valve guide inner diameter.
b. Check that clearance is within specification.
Valve to valve guide clearance standard
Intake 0.020 - 0.053 mm (0.0008 - 0.0021 inch)
Exhaust 0.040 - 0.073 mm (0.0016 - 0.0029 inch)
Valve to valve guide clearance limit
Intake 0.08 mm (0.0031 inch)
Exhaust 0.1 mm (0.004 inch)
c. 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 inch)] valve guide.
1. To remove valve guide, heat cylinder head to 110° to 130°C (230° to 266°F) by soaking in heated oil.
2. Drive out the valve guide with a press [under a 20 kN (2.2 US ton) pressure] or hammer and suitable tool.
3. 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 inch) intake and exhaust
4. 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.
Projection "L" 12.6 - 12.8 mm (0.496 - 0.504 inch)
5. 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 inch)
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
1. 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.
2. Ream cylinder head recess for service valve seat.
Oversize 0.5 mm (0.020 inch)
Intake 38.500 - 38.516 mm (1.5157 - 1.5164 inch)
Exhaust 32.700 - 32.716 mm (1.2874 - 1.2880 inch)
Be sure to ream in circles concentric to the valve guide center.
This will enable valve seat to fit correctly.
3. Heat cylinder head to 110° to 130°C (230° to 266°F) by soaking in heated oil.
4. Press fit valve seat until it seats on the bottom.
5. Cut or grind valve seat using suitable tool to the specified dimensions.
6. After cutting, lap valve seat with abrasive compound.
7. Check valve seating condition.
Seat face angle "a" 45° 15 - 45° 45 degrees/minutes
Contacting width "W" for intake 1.09 - 1.31 mm (0.0429 - 0.0516 inch)
Contacting width "W" for exhaust 1.29 - 1.51 mm (0.0508 - 0.0594 inch)
8. 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 seat resurface limit "L" intake 41.07 - 41.67 mm (1.6169 - 1.6405 inch)
Valve seat resurface limit "L" exhaust 41.00 - 41.60 mm (1.6142 - 1.6378 inch)
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 inch)
VALVE SPRING DIMENSIONS AND VALVE SPRING PRESSURE LOAD
Check valve spring pressure at specified spring height.
Standard 166 - 188 N (16.9 - 19.2 kg, 37.3 = 42.3 lbs.) at height 37.0 mm (1.457 inch)
Limit 373 - 418 N (38.0 - 42.6 kg, 83.9 - 94.0 lbs.) at height 27.2 mm (1.071 inch)
If it is not within specifications, replace the spring.
Valve Spring