Disassembly, Inspection and Assembly
Note: When installing sliding parts such as rocker arms and camshaft, be sure to apply engine oil on the sliding surfaces. When installing welch plug, apply sealant.
DISASSEMBLY
1. Remove camshaft locate plate.
2. Remove camshaft and camshaft oil seal.
3. Remove valve components as shown in image.
4. Remove valve oil seals.
INSPECTION
CYLINDER HEAD DISTORTION
Cylinder head distortion:
Less than 0.1 mm (0.004 in)
Note: If beyond the specified limit, resurface it.
Nominal cylinder head height:
116.6 - 117.0 mm (4.591 - 4.606 in)
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 in)
Note: After resurfacing the cylinder head, check that camshaft rotates freely by hand with cylinder block assembled.
VALVE GUIDE CLEARANCE
Valve guide clearance should be measured parallel with rocker arm. (Generally, a large amount of wear occurs in this direction.)
Stem to guide clearance:
Maximum limit
0.10 mm (0.0039 in)
Maximum allowable deflection
(Dial indicator reading)
0.2 mm (0.008 in)
^ To determine either valve or valve guide replacement, measure valve stem diameter and valve guide bore.
VALVE GUIDE REPLACEMENT
1. To remove valve guide, heat cylinder head to 150 to 160°C (302 to 320°F).
2. Drive out valve guide with a press [under a 20 kN (2t, 2.2 US ton, 2.0 Imp ton) pressure] or hammer and suitable tool.
3. Ream cylinder head valve guide hole.
Cylinder head valve guide hole diameter "a"
[For 0.2 mm (0.008 in) oversize]: mm (in)
11.185 - 11.196(0.4404 - 0.4408)
4. Heat cylinder head to 150 to 160°C (302 to 320°F) and press service valve guide onto cylinder head.
5. Ream valve guide.
Finished size: mm (in) 7.000 - 7.018 (0.2756 - 0.2763)
VALVE SEATS
Check valve seats for any evidence of pitting at valve contact surface, and reseat or replace if worn out excessively.
^ When repairing valve seats, check valve and valve guide for wear beforehand. If worn, replace them. Then correct valve seat.
^ The cutting should be done with both hands for uniform cutting.
REPLACING VALVE SEAT FOR SERVICE PARTS
1. Bore out old seat until it collapses.
Note: 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 the cylinder head recess.
Reaming bore for service valve seat
[Oversize 0.5 mm (0.020 in)]
Intake
43.500 - 43.516 mm (1.7126 - 1.7132 in)
Exhaust
37.500 - 37.516 mm (1.4764 - 1.4770 in)
Caution: Reaming should be done to the concentric circles around the valve guide center so that valve seat will have the correct fit.
3. Heat cylinder head to a temperature of 150 to 160°C (302 to 320°F).
4. Press fit seat until it seats on the bottom.
5. Wait until temperature of cylinder head reaches room temperature.
6. Cut or grind valve seat using suitable tool at the specified dimensions.
7. After cutting, lap valve seat with a lapping compound.
8. Check contact condition of valve seat.
CAMSHAFT JOURNAL CLEARANCE
1. Measure the inner diameter of camshaft bearing.
Standard inner diameter:
46.000 - 46.016 mm (1.8110 - 1.8116 in)
2. Measure the outer diameter of camshaft journal.
Standard outer diameter
#1 - #4 journal:
45.935 - 45.955 mm (1.8085 - 1.8092 in)
#5 journal:
45.915 - 45.935 mm (1.8077 - 1.8085 in)
If the clearance is greater than the maximum, replace camshaft and/or cylinder head.
Maximum clearance:
0.10 mm (0.0039 in)
CAMSHAFT RUNOUT
Camshaft runout [T.I.R. (Total Indicator Reading)]
Limit 0.05 mm (0.0020 in)
Note: It beyond the limit, replace.
CAMSHAFT CAM HEIGHT
Standard cam height:
Intake
37.675 - 37.755 mm (1.4833 - 1.4864 in)
Exhaust
38.281 - 38.361 mm (1.5071 - 1.5103 in)
Cam wear:
Limit 0.2 mm (0.008 in)
Note: If wear is beyond the limit, replace.
CAMSHAFT VISUAL CHECK
Check camshaft for scratches, seizure and wear.
CAMSHAFT END PLAY
1. Install camshaft and locate plate in cylinder head.
2. Measure camshaft end play. Camshaft end play:
Standard 0.07-0.14 mm (0.0028 - 0.0055 in)
Limit 0.2 mm (0.008 in)
CAMSHAFT SPROCKET RUNOUT
Install sprocket on camshaft and check for runout.
If runout exceeds the specified limit, replace camshaft sprocket.
Runout (Total indicator reading):
Limit 0.05 mm (0.0020 in)
VALVE DIMENSIONS
Check dimensions in each valve. When valve head has been worn down to 0.5 mm (0.020 in) in margin thickness, replace the valve.
Grinding allowance for valve stem tip is 0.2 mm (0.008 in) or less.
VALVE SPRING SQUARENESS
Out-of-square "S":
Outer
Less than 2.2 mm (0.087 in)
Inner
Less than 1.9 mm (0.075 in)
VALVE SPRING PRESSURE LOAD
Refer to Valve Spring.
ROCKER SHAFT AND ROCKER ARM
1. Draw all rocker arms from rocker shaft.
CAUTION:
a. Hydraulic lash adjuster is installed in each rocker arm. If the hydraulic lash adjuster is kept lying on its side, even when installed in the rocker arm, there is a risk of air entering the valve lifter. During storage, always set the rocker arm straight up, or when on its side, have it coated with oil.
b. Do not remove the hydraulic lash adjuster from the rocker arm except when exchanging it.
c. Do not disassemble the hydraulic lash adjuster.
2. Check rocker shafts for scratches, seizure and wear.
3. Check outer diameter of rocker shaft.
Diameter mm (in):
19.979 - 20.000 (0.7866 0.7874)
4. Check inner diameter of rocker arm.
Diameter mm (in):
20.007 - 20.028 (0.7877 - 0.7885)
Rocker arm to shaft clearance mm (in):
0.007 - 0.049 (0.0003 - 0.0019)
Note: Keep rocker arm with hydraulic lash adjuster standing to avoid mixing air into hydraulic lash adjuster at checking.
ASSEMBLY
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.
2. Install camshaft.
3. Install camshaft locate plate.
Tighten: Locate plate bolt
78-88N.m (8.0 9.0 kg-m, 58 65 ft-lb)
4. Apply engine oil to camshaft oil seal and install it in place.
^ Always use new camshaft oil seal.
^ When tightening locate plate, apply a wooden block to a suitably positioned cam so as not to turn camshaft together.