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2.3.1 Cylinder Head And Valves (Continued)
2.3.1.g Correcting Valve and Valve Seat
NOTE
Before correcting the valve seat, make certain
that the valve and valve guide are within factory
specifications.
After correcting the valve seat, be sure to check
the valve recession.
(A) Correcting the Valve
1. Correct the valve with a valve grinder.
Valve Face Angle
Factory
Specification
0.785 rad.
45
°
(B) Correcting the Valve Seat
1. Slightly correct the valve seat surface with a 0.785
rad. (45
°
) valve seat cutter.
2. Reinsert the valve, check the contact pattern with
prussian blue. A valve seat width should be approxi-
mately 70% of the total valve contact area. See (
A
) in
the illustration
3. Resurface the seat surface with a 0.262 rad. (15
°
)
valve seat cutter to the valve seat so that (
a
) equals
(
b
) in the illustration.
4. Grind the seat with a 0.785 rad (45
°
) valve seat cutter
again, and visually recheck the contact between the
valve and the seat.
5. Repeat steps 3 and 4 until the correct contact is
achieved.
6. Continue lapping until the seated width becomes
more than 70% of the total contact area.
Valve Seat Angle
Factory
Specification
0.785 rad.
45
°
1. Valve Seat Cutter
A
. Check Contact
B
. Correct Seat Width
C
. Correct Seat Surface
D
. Check Contact
a
. Identical Dimensions
b
. Valve Seat Width
c
. 0.262 rad (15
°
)
d
0.785 rad (45
°
)
2.3.1.h Valve Lapping
1. Apply compound evenly to the valve lapping surface.
2. Insert the valve into the valve guide. Lap the valve
onto its seat with a valve lapper.
3. After lapping the valve, wash the compound away
and apply oil, then repeat valve lapping with oil.
4. Apply prussian blue to the contact surface to check
the contact pattern. If it is less than 70%, repeat valve
lapping again.
NOTE
When valve lapping is performed, be sure to
check the valve recession and adjust the valve
clearance after assembling the valve.
