Disassembly and Assembly
Disassembly
CAUTION:
^ When installing camshaft and oil seal, lubricate contacting surfaces with new engine oil.
^ When tightening cylinder head bolts, camshaft sprocket bolts and camshaft bracket bolts, lubricate bolt threads and seat surfaces with new engine oil.
^ Attach tags to valve lifters so as not to mix them up.
1. Remove valve components with Tool.
2. Remove valve oil seal with a suitable tool.
Inspection
CYLINDER HEAD DISTORTION
^ Clean surface of cylinder head.
^ Use a reliable straightedge and feeler gauge to check the flatness of cylinder head mating surface.
^ Check along six positions shown in figure.
Head surface flatness:
Standard: Less than 0.03 mm (0.0012 inch)
Limit: 0.1 mm (0.004 inch)
If beyond the specified limit, replace or resurface it.
Resurfacing limit:
The limit for cylinder head resurfacing is determined by the amount of cylinder block resurfacing.
Amount of cylinder head resurfacing is "A".
Amount of cylinder block resurfacing is "B".
The maximum limit is as follows: A + B = 0.2 mm (0.008 inch)
After resurfacing cylinder head, check that camshaft rotates freely by hand. If resistance is felt, replace cylinder head.
Nominal cylinder head height: 117.8 - 118.0 mm (4.638 - 4.646 inch)
CAMSHAFT VISUAL CHECK
Check camshaft for scratches, seizure and wear.
CAMSHAFT RUNOUT
1. Measure camshaft runout at the center journal.
Runout (Total indicator reading):
Standard: Less than 0.02 mm (0.0008 inch)
Limit: 0.1 mm (0.004 inch)
2. If it exceeds the limit, replace camshaft.
CAMSHAFT CAM HEIGHT
1. Measure camshaft cam height. Standard cam height:
Intake: 40.610 - 40.800 mm (1.5988 - 1.6063 inch)
Exhaust: 40.056 - 40.246 mm (1.5770 - 1.5845 inch)
Cam wear limit: 0.20 mm (0.0079 inch)
2. If wear is beyond the limit, replace camshaft.
CAMSHAFT JOURNAL CLEARANCE
1. Install camshaft bracket and tighten bolts to the specified torque.
2. Measure inner diameter of camshaft bearing.
Standard inner diameter:
No. 1 bearing: 28.000 - 28.021 mm (1.1024 - 1.1032 inch)
No. 2 to No. 5 bearings: 24.000 - 24.021 mm (0.9449 - 0.9457 inch)
3. Measure outer diameter of camshaft journal.
Standard outer diameter:
No. 1 journal: 27.935 - 27.955 mm (1.0998 - 1.1006 inch)
No. 2 to No. 5 journals: 23.935 - 23.955 mm (0.9423 - 0.9431 inch)
4. If clearance exceeds the limit, replace camshaft and/or cylinder head.
Camshaft journal clearance:
Standard: 0.045 - 0.086 mm (0.0018 - 0.0034 inch)
Limit: 0.15 mm (0.0059 inch)
CAMSHAFT END PLAY
1. Install camshaft in cylinder head.
2. Measure camshaft end play.
Camshaft end play:
Standard: 0.115 - 0.188 mm (0.0045 - 0.0074 inch)
Limit: 0.20 mm (0.0079 inch)
3. If limit is exceeded, replace camshaft and remeasure end play.
^ If limit is still exceeded after replacing camshaft, replace cylinder head.
CAMSHAFT SPROCKET RUNOUT
1. Install sprocket on camshaft.
2. Measure camshaft sprocket runout.
Runout (Total indicator reading): Limit 0.15 mm (0.0059 inch)
3. If it exceeds the limit, replace camshaft sprocket.
VALVE GUIDE CLEARANCE
1. Measure valve deflection as shown in figure. (Valve and valve guide wear the most in this direction.)
Valve deflection limit (Dial gauge reading):
Intake & Exhaust: 0.2 mm (0.008 inch)
2. If it exceeds the limit, check valve to valve guide clearance.
a. Measure valve stem diameter and valve guide inner diameter. Calculate valve to valve guide clearance.
b. Valve stem to valve guide clearance = valve guide inner diameter - valve stem diameter.
c. Check that clearance is within specification.
^ If it exceeds the limit, replace valve and remeasure clearance.
^ If limit is still exceeded after replacing valve, replace valve guide.
VALVE GUIDE REPLACEMENT
1. To remove valve guide, heat cylinder head to 110 to 130°C (230 to 266°F).
2. Drive out valve guide with a press [under a 20 kN (2 ton, 2.2 US ton, 2.0 Imp ton) pressure] or hammer and suitable tool.
3. Ream cylinder head valve guide hole.
Valve guide hole diameter (for service parts):
Intake & Exhaust: 9.685 - 9.696 mm (0.3813 - 0.3817 inch)
4. Heat cylinder head to 110 to 130°C (230 to 266°F) and press service valve guide into cylinder head.
Projection "L": 11.5 - 11.7 mm (0.453 - 0.461 inch)
5. Ream valve guide.
Finished size:
Intake & Exhaust: 5.500 - 5.515 mm (0.2165 - 0.2171 inch)
VALVE SEATS
Check valve seats for pitting at contact surface. Resurface or replace if excessively worn.
^ Before repairing valve seats, check valve and valve guide for wear. If they have worn, replace them. Then correct valve seat.
^ Use both hands to cut uniformly.
REPLACING VALVE SEAT FOR SERVICE PARTS
1. Bore out old seat until it collapses. Set machine depth stop so that boring cannot contact the bottom face of seat recess in cylinder head.
2. Ream cylinder head recess.
Reaming bore for service valve seat
Oversize [0.5 mm (0.020 inch)]:
Intake: 31.500 - 31.516 mm (1.2402 - 1.2408 inch)
Exhaust: 26.500 - 26.516 mm (1.0433 - 1.0439 inch)
Use the valve guide center for reaming to ensure valve seat will have the correct fit.
3. Heat cylinder head to 110 to 130°C (230 to 266°F).
4. Press fit valve seat until it seats on the bottom.
5. Cut or grind valve seat using suitable tool to the specified dimensions as shown in "VALVE SEAT". Refer to Engine; Specifications.
6. After cutting, lap valve seat with abrasive compound.
7. Check valve seating condition.
Seat face angle "a": 44°53' - 45°07'
Contacting width "W":
Intake: 1.06 - 1.34 mm (0.0417 - 0.0528 inch)
Exhaust: 1.34 - 1.63 mm (0.0528 - 0.0642 inch)
8. Use a depth gauge to measure the distance "L" 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 above to correct it. If the distance is longer, replace the valve seat.
Valve seat resurface limit:
Intake: 35.95 - 36.55 mm (1.4154 - 1.4390 inch)
Exhaust: 35.92 - 36.52 mm (1.4142 - 1.4378 inch)
VALVE DIMENSIONS
Check dimensions of each valve. Refer to "VALVE", at Engine; Specifications for dimensions.
When valve head has been worn down to 0.5 mm (0.020 inch) in margin thickness, replace valve.
Grinding allowance for valve stem tip is 0.2 mm (0.008 inch) or less.
VALVE SPRING
Squareness
1. Measure dimension "S".
Out-of-square "S": Less than 1.75 mm (0.0689 inch)
2. If it exceeds the limit, replace spring.
Pressure
Check valve spring pressure at specified spring height.
Pressure.
Standard: 370.0 N (37.73 kg, 83.19 lbs.) at 23.64 mm (0.9307 inch)
Limit: More than 347.8 N 135.46 kg, 78.19 lbs.) at 23.64 mm (0.9307 inch)
If not within specification, replace spring.
VALVE LIFTER AND VALVE SHIM
1. Check contact and sliding surfaces for wear or scratches.
2. Check diameter of valve lifter and valve lifter guide bore.
Valve lifter outside diameter: 29.960 - 29.975 mm (1.1795 - 1.1801 inch)
Lifter guide inside diameter: 30.000 - 30.021 mm (1.1811 - 1.1819 inch)
Clearance between valve lifter and valve lifter guide: 0.025 - 0.065 mm (0.0010 - 0.0026 inch)
If it exceeds the limit, replace valve lifter or cylinder head which exceeds the standard diameter tolerance.
Reassembly
1. Install valve component parts.
^ Always use new valve oil seal.
^ Before installing valve oil seal, install valve spring seat.
^ After installing valve components, tap valve stem tip with a plastic hammer to assure a proper fit.
^ Install valve spring (narrow pitch at both ends of spring) with either end toward cylinder head.