Disassembly and Assembly
Disassembly
CAUTION:
- When installing sliding parts such as rocker arms, camshaft and oil seal, be sure to apply new engine oil on their sliding surfaces.
- When tightening cylinder head bolts and rocker shaft bolts, apply new engine oil to thread portions and seat surfaces of bolts.
- If hydraulic valve lifter is kept on its side, there is a risk of air entering it. After removal, always set hydraulic valve lifter straight up, or when laying it on its side, have it soak in new engine oil.
- Do not disassemble hydraulic valve lifter.
- Attach tags to valve lifters so as not to mix them up.
1. Remove exhaust manifolds from cylinder head.
2. Remove rocker shafts with rocker arms.
Bolts should be loosened in two or three steps.
3. Remove hydraulic valve lifters and lifter guide.
- Hold hydraulic valve lifters with wire so that they will not drop from lifter guide.
4. Remove oil seal and camshaft.
- Before removing camshaft, measure camshaft end play.
5. Remove valve components with Tool.
6. Remove valve oil seals with Tool or suitable tool.
Inspection
CYLINDER HEAD DISTORTION
Head surface flatness: Less than 0.1 mm (0.004 inch)
If beyond the specified limit, resurface it or replace it.
Resurfacing limit: The resurfacing limit of cylinder head is determined by the cylinder block resurfacing in an engine.
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, cylinder head must be replaced.
Nominal cylinder head height: 106.8 - 107.2 mm (4.205 - 4.220 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):
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: 38.943 - 39.133 mm (1.5332 - 1.5407 inch)
Exhaust: 38.943 - 39.133 mm (1.5332 - 1.5407 inch)
Cam wear limit: 0.15 mm (0.0059 inch)
If wear is beyond the limit, replace camshaft.
CAMSHAFT JOURNAL CLEARANCE
1. Measure inner diameter of camshaft bearing.
Standard inner diameter:
A 47.000 - 47.025 mm (1.8504 - 1.8514 inch)
B 42.500 - 42.525 mm (1.6732 - 1.6742 inch)
C 48.000 - 48.025 mm (1.8898 - 1.8907 inch)
2. Measure outer diameter of camshaft journal.
Standard outer diameter:
A 46.920 - 46.940 mm (1.8472 - 1.8480 inch)
B 42.420 - 42.440 mm (1.6701 - 1.6709 inch)
C 47.920 - 47.940 mm (1.8866 - 1.8874 inch)
3. If clearance exceeds the limit, replace camshaft and/or cylinder head.
Camshaft journal clearance limit: 0.15 mm (0.0059 inch)
CAMSHAFT END PLAY
1. Install camshaft and locate plate in cylinder head.
2. Measure camshaft end play.
Camshaft end play:
Standard 0.03 - 0.06 mm (0.0012 - 0.0024 inch)
3. If it is out of the specified range, select thickness of camshaft locate plate to obtain standard specified end play.
Example: When camshaft end play is 0.08 mm (0.0031 inch) with camshaft locate plate 2, replace camshaft locate plate 2 with camshaft locate plate 3 to set the end play at 0.05 mm (0.0020 inch).
CAMSHAFT SPROCKET RUNOUT
1. Install sprocket on camshaft.
2. Measure camshaft sprocket runout.
Runout (Total indicator reading):
Limit 0.1 mm (0.004 inch)
3. If it exceeds the limit, replace camshaft sprocket.
VALVE GUIDE CLEARANCE
1. Measure valve deflection in a right-angled direction with camshaft. (Valve and valve guide mostly wear in this direction.)
Valve deflection limit (Dial gauge reading): 0.20 mm (0.0079 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:
Intake: 0.020 - 0.053 mm (0.0008 - 0.0021 inch)
Exhaust: 0.040 - 0.049 mm (0.0016 - 0.0019 inch)
Limit: 0.10 mm (0.0039 inch)
c. If it exceeds the limit, replace valve or valve guide.
VALVE GUIDE REPLACEMENT
1. To remove valve guide, heat cylinder head to 150 to 160°C (302 to 320°F) by soaking in heated oil.
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: 11.175 - 11.196 mm (0.4400 - 0.4408 inch)
Exhaust: 12.175 - 12.196 mm (0.4793 - 0.4802 inch)
4. Heat cylinder head to 150 to 160°C (302 to 320°F) and press service valve guide onto cylinder head.
Projection "L": 13.2 - 13.4 mm (0.520 - 0.528 inch)
5. Ream valve guide.
Finished size:
Intake: 7.000 - 7.018 mm (0.2756 - 0.2763 inch)
Exhaust: 8.000 - 8.011 mm (0.3150 - 0.3154 inch)
VALVE SEATS
Check valve seats for any evidence of pitting at valve contact surface, and reseat or replace if it has worn out excessively.
- 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. The machine depth stop should be set so that boring cannot continue beyond the bottom face of the seat recess in cylinder head.
2. Ream cylinder head recess.
Reaming bore for service valve seat
Oversize [0.5 mm (0.020 inch)]:
Intake: 44.500 - 44.516 mm (1.7520 - 1.7526 inch)
Exhaust: 37.500 - 37.516 mm (1.4764 - 1.4770 inch)
Reaming should be done in circles concentric to the valve guide center so that valve seat will have the correct fit.
3. Heat cylinder head to 150 to 160°C (302 to 320°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 at the specified dimensions as shown. Refer to Engine; Specifications.
6. After cutting, lap valve seat with abrasive compound.
7. Check valve seating condition.
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 above to adjust it. If it is longer, replace the valve seat with a new one.
Intake: 44.7 - 44.9 mm (1.760 - 1.768 inch)
Exhaust: 45.4 - 45.6 mm (1.787 - 1.795 inch)
VALVE DIMENSIONS
Check dimensions in each valve. For dimensions, refer to specifications. 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 "S" dimension.
Less than 2.2 mm (0.087 inch)
2. If it exceeds the limit, replace spring.
Pressure
Check valve spring pressure.
Standard pressure: 790 N (80.6 kg, 178 lbs.) at 30.0 mm (1.181 inch)
Limit pressure: More than 733 N (74.7 kg, 165 lbs.) at 30.0 mm (1.181 inch)
If it exceeds the limit, replace spring.
ROCKER SHAFT AND ROCKER ARM
1. Check rocker shafts for scratches, seizure and wear.
2. Check outer diameter of rocker shaft.
Diameter: 17.979 - 18.000 mm (0.7078 - 0.7087 inch)
3. Check inner diameter of rocker arm.
Diameter: 18.007 - 18.028 mm (0.7089 - 0.7098 inch)
Rocker arm to shaft clearance: 0.007 - 0.049 mm (0.0003 - 0.0019 inch)
- Keep rocker arm with hydraulic valve lifter standing to prevent air from entering hydraulic valve lifter when checking.
HYDRAULIC VALVE LIFTER
1. Check contact and sliding surfaces for wear or scratches.
2. Check diameter of valve lifter.
Outer diameter: 15.947 - 15.957 mm (0.6278 - 0.6282 inch)
3. Check valve lifter guide inner diameter.
Inner diameter: 16.000 - 16.013 mm (0.6299 - 0.6304 inch)
Standard clearance between valve lifter and lifter guide: 0.043 - 0.066 mm (0.0017 - 0.0026 inch)
Reassembly
CAUTION:
- When installing sliding parts such as rocker arms, camshaft and oil seal, be sure to apply new engine oil on their sliding surfaces.
- When tightening cylinder head bolts and rocker shaft bolts, apply new engine oil to thread portions and seat surfaces of bolts.
- If hydraulic valve lifter is kept on its side, there is a risk of air entering it. After removal, always set hydraulic valve lifter straight up, or when laying it on its side, have it soak in new engine oil.
- Do not disassemble hydraulic valve lifter.
- Attach tags to valve lifters so as not to mix them up.
1. Install valve component parts.
- Always use new valve oil seal.
- Before installing valve oil seal, install inner valve spring seat.
- Install outer valve spring (uneven pitch type) with its narrow pitch side toward cylinder head side.
- After installing valve component parts, use plastic hammer to lightly tap valve stem tip to assure a proper fit.
2. Install camshafts, locate plates and cylinder head rear covers.
- Set knock pin of camshaft at the top.
3. Install valve lifters into valve lifter guide.
- Assemble valve lifters to their original position and hold all valve lifters with wire to prevent lifters from falling off.
- After installing, remove the wire.
4. Install rocker shafts with rocker arms.
- Tighten bolts gradually in two or three stages.
- Before tightening, be sure to set camshaft the lobe at the position where lobe is not lifted.
a. Set No. 1 piston at TDC on its compression stroke and tighten rocker shaft bolts for No. 2, No. 4 and No. 6 cylinders.
b. Set No. 4 piston at TDC on its compression stroke and tighten rocker shaft bolts for No 1, No. 3 and No. 5 cylinders.
c. Install exhaust manifold to cylinder head in reverse order of removal.