Valves and Cylinder Head Components Inspection
Valve Guides
Using a micrometer and bore gauge, take diameter readings on valve stems and guides to check stem-to-guide clearance. Be sure to take reading at more than one place along the length of each stem and guide.
If clearance exceeds specification, replace valve and valve guide.
Valve stem-to-guide clearance
In: 0.015 – 0.049 mm (0.00059 – 0.00192 in.)
Ex: 0.029 – 0.063 mm (0.00115 – 0.00248 in.)
Valve stem diameter [A]
In: 5.969 – 5.985 mm (0.23500 – 0.23562 in.)
Ex: 5.955 – 5.971 mm (0.23445 – 0.23507 in.)
Valve guide bore [B]
In and Ex: 6.000 – 6.018 mm (0.23622 – 0.23692 in.)
Remove all carbon from valves.
Inspect each valve for wear, burn or distortion at its face and stem end, as necessary, replace it.
Measure length “a” of valve.
If measured length is out of specification, replace valve.
Valve length “a”
In: 100.73 – 101.17 mm (3.9658 – 3.9830 in.)
Ex: 100.53 – 100.97 mm (3.9579 – 3.9751 in.)
Measure diameter “b” of valve.
If measured diameter is out of specification, replace valve.
Valve head diameter “b”
In: 33.38 – 33.62 mm (1.3142 – 1.3236 in.)
Ex: 28.88 – 29.12 mm (1.1370 – 1.1464 in.)
Valve seat repair:
A valve seat not producing a uniform contact with its valve or showing width of seating contact that is out of specified range must be repaired by regrinding or by cutting and regrinding and finished by lapping.
a. Valve Seat:
Use valve seat cutters (1) to make a cut as illustrated in the figure.
Seat width
“a”: 1.8 mm (0.071 in.)
Seat angle
“b”: 89° 30'
b. Valve Lapping:
Lap valve on seat in two steps, first with coarse size lapping compound applied to face and the second with fine-size compound, each time using valve lapper according to usual lapping method.
Cylinder Head
Remove all carbon deposits from combustion chambers.
Do not use any sharp-edged tool to scrape off carbon deposits. Be careful not to scuff or nick metal surfaces when decarboning. The same applies to valves and valve seats, too.
Check cylinder head for cracks on intake and exhaust ports, combustion chambers, and head surface.
Using a straightedge and thickness gauge, check flatness of gasketed surface at a total of 2 locations. If distortion limit, given below, is exceeded, replace cylinder head.
Limit of distortion for surface of cylinder head piston side:
0.05 mm (0.00197 in.)
Distortion of manifold seating faces:
Check seating faces of cylinder head for manifolds, using a straightedge and thickness gauge, in order to determine whether these faces should be corrected or cylinder head replaced.
Limit of distortion for surface of cylinder head exhaust: manifolds sides
0.2 mm (0.008 in.)
Measure cylinder head height “a”.
If measured height is below its specification, replace cylinder head.
Cylinder head height “a”:
127 mm (5.00 in.)
Valve Springs
Referring to data given below, check to be sure that each spring is in sound condition, free of any evidence of breakage or weakening. Remember, weakened valve springs can cause chatter, not to mention possibility of reducing power output due to gas leakage caused by decreased seating pressure.
Valve spring free length (In and Ex) “a”:
43.31 mm (1.7051 in.)
Valve spring preload (In and Ex):
23 N (2.3 kg) for 33.80 mm (5.0 lb/ 1.3307 in.)
50 N (5.0 kg) for 24.80 mm (11.0 lb/ 0.9764 in.)
Max. Valve Lift
1) Install valve, tappet and camshaft referring to “Installation” under Valves and Cylinder Head Assembly Removal and Installation:K9K .
2) Measure valve lift using dial gauge as shown in the figure.
If measured valve lift is found to exceed its limit, adjust valve lash (clearance) referring to Valve Lash (Clearance) Inspection:K9K .
Special Tool
(A) : 09910–26510 /OUT0000005
Max. valve lift
In: 8.015 mm (0.31555 In.)
Ex: 8.595 mm (0.33839 In.)
2. Intake valve 3. Exhaust valve