Valve and Valve Guide Inspection
Valves and Valve Guides InspectionValve Guide
Valve stem-to-guide clearance
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 limit, replace valve and valve guide.
Valve stem and valve guide specification
Valve stem end deflection
If bore gauge is not available, check end deflection of valve stem with a dial gauge instead. Move stem end in directions (1) and (2) to measure end deflection.
If deflection exceeds its limit, replace valve stem and valve guide.
Valve stem end deflection limit
In: 0.14 mm (0.005 in.)
Ex: 0.18 mm (0.007 in.)
Valve
Visual inspection
^ Remove all carbon from valves.
^ Inspect each valve for wear, burn or distortion at its face and stem end, as necessary, replace it.
^ Inspect valve stem end face for pitting and wear. If pitting or wear is found there, valve stem end may be resurfaced, but not too much to grind off its chamber. When it is worn out too much that its chamber is gone, replace valve.
Valve head thickness
Measure thickness "a" of valve head. If measured thickness exceeds limit, replace valve.
Valve head thickness "a"
Intake
Standard: 1.25 - 1.55 mm (0.049 - 0.061 in.)
Limit: 0.9 mm (0.035 in.)
Exhaust
Standard: 1.45 - 1.75 mm (0.057 - 0.069 in.)
Limit: 1.1 mm (0.04 in.)
Valve head radial runout
Check each valve for radial runout with a dial gauge and "V" block. To check runout, rotate valve slowly. If runout exceeds its limit, replace valve.
Valve head radial runout Limit: 0.08 mm (0.003 in.)
Seating contact width
Create contact pattern on each valve in the usual manner, i.e., by giving uniform coat of marking compound to valve seat and by rotatingly tapping seat with valve head. Valve lapper (tool used in valve lapping) must be used.
Pattern produced on seating face of valve must be a continuous ring without any break, and the width of pattern must be within specified range.
Standard seating width "a" revealed by contact pattern on valve face Intake and Exhaust: 1.0 - 1.4 mm (0.0389 - 0.0551 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.
1. Exhaust valve seat:
Use valve seat cutters (1) to make two cuts as illustrated in the figure. Two cutters must be used: the first for making 150 angle, and the second for making 450 angle. The second cut must be made to produce desired seat width.
Seat width for exhaust valve seat
"a": 1.0 - 1.4 mm (0.0389 - 0.0551 in.)
2. Intake valve seat:
Use valve seat cutters (1) to make three cuts as illustrated in the figure. Three cutters must be used: the 1st for making 25° angle, the 2nd for making 60° angle, and 3rd for making 45° angle. The 3rd cut (45°) must be made to produce desired seat width.
Seat width for intake valve seat
"b": 1.0 - 1.4 mm (0.0389 - 0.0551 in.)
3. 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.
