Service manual

G420F(FE) Service Manual Chapter 3. Engine Mechanical System 70
VALVE SEAT RING REPLACEMENT
1. If the valve seat insert is excessively worn, cut the
insert ring wall as shown in the illustration “A”
using a valve seat cutter at a normal temperature.
2. After removing the seat ring, Cut the seat insert
bore as same size as the following table as
shown in the illustration “A” using a reamer or
cutter.
3. Heat the cylinder head to 250°C and press-fit the
oversize seat.
At this time the oversize seat ring maintains a
normal room temperature.
After installing a new valve seat, correct the valve
seat surface.
Valve seat ring oversize
Item Size(mm) Size mark
Cylinder insert height
H (mm)
Cylinder head I.D
(mm)
0.3 OS 30 7.5 ~ 7.7 33.330 ~ 33.325
Intake valve seat ring
0.6 OS 60 7.8 ~ 8.0 33.600 ~ 33.625
0.3 OS 30 7.9 ~ 8.1 28.800 ~ 28.821
Exhaust valve seat ring
0.6 OS 60 8.2 ~ 8.4 29.100 ~ 29.121