Cylinder Head Assembly: Service and Repair

DISASSEMBLY
1. Remove rocker shaft with rocker arms.
The bolts should be loosened in two or three stages.
Keep rocker shaft components in correct order.





2. Remove camshaft from front side.





3. Remove valve component parts with Tool.








INSPECTION

CYLINDER HEAD DISTORTION
Cylinder head distortion:
Less than 0.1 mm (0.004 in)
If beyond the specified limit, replace it or resurface 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 in)
After resurfacing the cylinder head, check that camshaft rotates freely by hand. If resistance is felt, the cylinder head must be replaced.
Cylinder head height (Nominal):
120 ± 0.1 mm (4.724 ± 0.004 in)





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 the correct or replacement part, measure valve stem diameter and valve guide bore. For dimensions, refer to Specifications. Specifications





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 hammer and suitable tool.





3. Ream cylinder head valve guide hole. (at room temperature)
Valve guide hole inner diameter
(For service parts): mm (in)
12.200 - 12.211(0.4803 - 0.4807)





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. (at room temperature)
Finished size:
7.005 - 7.020 mm (0.2758 - 0.2764 in)





VALVE SEATS
Check valve 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. 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 in)]:
Intake:
38.50-38.52 mm (1.5157 - 1.5165 in)
Exhaust:
29.60-29.61 mm (1.1654 - 1.1657 in)
Reaming should be done to the concentric circles to 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 insert until it seats on the bottom.





5. Cut or grind valve seat using suitable tool at the specified dimensions as shown in Specifications.
6. After cutting, lap valve seat with a lapping compound.
7. Check contact condition of valve seat.

CAMSHAFT VISUAL CHECK
Check camshaft for scratches, seizure and wear.





CAMSHAFT END PLAY
1. Install camshaft and front cover in cylinder head.
2. Measure camshaft end play.
Camshaft end play:
Limit 0.4 mm (0.016 in)





CAMSHAFT JOURNAL CLEARANCE
1. Measure the inside diameter of camshaft bearing.
Standard inner diameter:
42.000 - 42.025 mm (1.6535 - 1.6545 in)





2. Measure the outside diameter of camshaft journal.
Standard outer diameter:
No.1,3,5
41.949 - 41.965 mm (1.6515 - 1.6522 in)
No.2, 4
41.906 - 41.922 mm (1.6498 - 1.6505 in)
If the clearance is greater than the maximum, replace camshaft and/or cylinder head.

Maximum clearance:
No.1,3,5
0.15 mm (0.0059 in)
No.4, 6
0.20 mm (0.0079 in)





CAMSHAFT RUNOUT
Runout [T.l.R. (Total Indicator Reading)]
Limit 0.1 mm (0.004 in) at the center journal.
If beyond the limit, replace.





CAMSHAFT CAM HEIGHT
Standard cam height:
Intake
35.884 - 36.134 mm (1.4128 - 1.4226 in)
Exhaust
35.64-35.89 mm (1.4031 - 1.4130 in)
Cam wear:
Limit 0.20 mm (0.0079 in)
If wear is beyond the limit, replace.





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 0.1 mm (0.004 in)





VALVE DIMENSIONS
Check dimensions in each valve. For dimensions, refer to Specifications. Specifications
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:
Less than 2.0 mm (0.079 in)





VALVE SPRING PRESSURE LOAD
Refer to Specifications. Specifications





ROCKER SHAFT AND ROCKER ARM
1. Check rocker shaft and rocker arms for scratches, seizure and wear.
2. Check outer diameter of rocker shaft.
Diameter mm (in):
19.979 - 20.000 (0.7866-0.7874)





3. Check inner diameter of rocker arm.
Diameter mm (in):
20.007 - 20.028 (0.7877 - 0.7885)
Rocker arm to shaft clearance:
0.007 - 0.049 (0.0003 - 0.0019)





ASSEMBLY
1. Install valve component parts.
^ Always use new valve oil seal. (Refer to OIL SEAL.) Valve
^ Before installing valve oil seal, install valve spring seat.
^ Install valve spring (uneven pitch type) with its narrow pitch side toward cylinder head side.
2. Install camshaft and upper front cover in cylinder head with new camshaft oil seal.
^ Refer to OIL SEAL. Valve





^ After installing camshaft, set knock pin upper side.





3. Install camshaft sprocket.
^ Align camshaft sprocket mark with upper front cover mark.





4. Align crankshaft sprocket mark with lower front cover mark.
5. Install intake manifold to cylinder head.
Intake manifold fixing nuts:
Tighten: 16 - 21 N.m (1.6 - 2.1 kg-m, 12- 15 ft-lb)

INSTALLATION
1. Install cylinder head with new gasket.
^ Be sure to install washers between cylinder head and bolts.





^ There are three kinds of cylinder head bolts with different lengths.
Bolt length "L":
(A): 95 mm (3.74 in)
(B): 110 mm(4.33 in)
(C): 80 mm (3.15 in)











2. Apply oil to the thread portion and seat surface of cylinder head bolts and tighten cylinder head bolts with washers.
Tightening procedure:
1st Tighten all bolts to 29 N.m (3.0 kg-m, 22 ft-lb)
2nd Tighten all bolts to 69 N.m (7.0 kg-m, 51 ft-lb)
3rd Loosen all bolts completely
4th Tighten all bolts to 29 N.m (3.0 kg-m, 22 ft-lb).
5th Tighten all bolts to 69 to 74 N-m (7.0 to 7.5 kg-m, 51 to 54 ft-lb) or if you have an angle wrench, turn each bolt clockwise the specified number of degrees.

Specified number of degrees.
(A): 45-50
(B): 55-60
(C): 40-45.