Inspection
Cylinder Head Distortion
- Clean mating 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, cylinder head must be replaced.
Nominal cylinder head height: 136.9 - 137.1 mm (5.390 - 5.398 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: 37.550 - 37.740 mm (1.4783 - 1.4858 inch)
Exhaust: 37.920 - 38.110 mm (1.4929 - 1.5004 inch)
Cam height wear limit: Intake & Exhaust: 0.2 mm (0.008 inch)
2. If wear is beyond the limit, replace camshaft.
Camshaft Journal Clearance
1. Install camshaft bracket and tighten bolts.
2. Measure inner diameter of camshaft bearing.
Standard inner diameter: 28.000 - 28.021 mm (1.1024 - 1.1032 inch)
3. Measure outer diameter of camshaft journal.
Standard outer diameter: 27.935 - 27.955 mm (1.0998 - 1.1006 inch)
4. Calculate camshaft journal clearance.
Camshaft journal clearance = standard inner diameter - standard outer diameter:
Standard: 0.045 - 0.090 mm (0.0018 - 0.0035 inch)
Limit: 0.15 mm (0.0059 inch)
5. If clearance exceeds the limit, replace camshaft and remeasure camshaft journal clearance.
- If clearance still exceeds the limit after replacing camshaft, replace cylinder head.
Camshaft End Play
1. Install camshaft in cylinder head.
2. Measure camshaft end play.
Camshaft end play:
Standard: 0.055 - 0.139 mm (0.0022 - 0.0055 inch)
Limit: 0.20 mm (0.0079 inch)
3. If end play exceeds the limit, replace camshaft and remeasure camshaft end play.
- If end play still exceeds the limit after replacing camshaft, replace cylinder head.
Camshaft Sprocket Runout
1. Install sprocket on camshaft.
2. Measure camshaft sprocket runout.
Runout (Total indicator reading) Limit: 0.25 mm (0.0098 inch)
3. If it exceeds the limit, replace camshaft sprocket.
Valve Guide Clearance
1. Measure valve deflection as shown in illustration. (Valve and valve guide mostly wear 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.
b. Calculate valve to valve guide clearance.
Valve to valve guide clearance = valve guide inner diameter - valve stem diameter:
Standard:
Intake 0.020 - 0.053 mm (0.0008 - 0.0021 inch)
Exhaust: 0.040 - 0.073 mm (0.0016 - 0.0029 inch)
Limit
Intake: 0.08 mm (0.0031 inch)
Exhaust: 0.1 mm (0.004 inch)
c. If it exceeds the limit, replace valve and remeasure clearance.
- If clearance still exceeds the limit 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 20kN [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: 10.175 - 10.196 mm (0.4006 - 0.4014 inch)
4. Heat cylinder head to 110 to 130°C (230 to 266°F) and press service valve guide into cylinder head.
Projection "L": 14.0 - 14.2 mm (0.551 - 0.559 inch)
5. Ream valve guide.
Finished size:
Intake & Exhaust: 6.000 - 6.018 mm (0.2362 - 0.2369 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 are 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 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: 35.500 - 35.516 mm (1.3976 - 1.3983 inch)
Exhaust: 31.500 - 31.516 mm (1.2402 - 1.2408 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 to the specified dimensions using a suitable tool.
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: 1.05 - 1.35 mm (0.0413 - 0.0531 inch)
Exhaust: 1.25 - 1.55 mm (0.0492 - 0.0610 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 above to adjust it.
If it is longer, replace the valve seat with a new one.
Valve seat resurface limit: 42.74 - 43.26 mm (1.6827 - 1.7031 inch)
Valve Dimensions
Check dimensions of each valve. 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 2.2 mm (0.087 inch)
2. If it exceeds the limit, replace spring.
Pressure
Check valve spring pressure at specified spring height.
Pressure:
Standard: 578.02 - 641.57 N (58.94 - 65.42 kg, 129.96 - 144.25 lb) at 30.0 mm (1.181 inch)
Limit: More than 549.2 N (56.0 kg, 123.5 lb) at 30.0 mm (1.181 inch)
If it exceeds the limit, replace spring.
Hydraulic Lash Adjuster
1. Check contact and sliding surfaces for wear or score.
2. Check diameter of lash adjuster.
Outer diameter: 16.980 - 16.993 mm (0.6685 - 0.6690 inch)
3. Check lash adjuster guide hole diameter.
Inner diameter: 17.000 - 17.020 mm (0.6693 - 0.6701 inch)
Standard clearance between lash adjuster and adjuster guide hole: 0.007 - 0.040 mm (0.0003 - 0.0016 inch)
Rocker Arm, Shim And Rocker Arm Guide
Check contact and sliding surfaces of rocker arms, shims and rocker arm guides for wear or score.