SECTION 10 - ENGINE
10-39
Op. 10 101 55
VALVE SEAT
Valve Seat Contact Width
If the contact width at 1 of the valve seat is more than
the allowable width, check the wear condition of the
valve guide first.
Using the seat cutters of 15°, 45°, and 75°, correct
the seat.
Intake
Standard Width: 0.06″ - 0.08″ (1.5 mm - 2.0 mm)
Allowable Limit: 0.098″ max. (2.5 mm)
Exhaust
Standard Width: 0.076″ - 0.085″ (1.94 mm - 2.16
mm)
Allowable Limit: 0.098″ max. (2.5 mm)
SH62052
53
Valve Seat Recess
If the recess depth, 1, is more than the allowable limit,
replace the valve seat (if fitted).
Standard Recess: 0.026″ - 0.037″ (0.65 mm -
0.95 mm)
Allowable Limit: 0.063″ max. (1.6 mm)
Replacement of valve seat insert (where fitted:)
Method 1: Using a gas burner, 1300° F to 1475° F
(700° C to 800° C), heat diagonally across the valve
seat insert. Leave in air for three to five minutes and
remove the valve seat insert by light tapping
(ensuring the head is not damaged).
Method 2: Machine the insert out, taking care not to
damage the head.
Clean up the insert bore and fit a new insert, using a
press 7,200 lbs. - 10,850 lbs. (1,000 kgf - 1,500 kgf)
and a suitable smooth surface tool. To assist the
process, chill the valve seat insert with liquid
nitrogen, etc., or heat the head to between 140° F to
212° F (60° C and 100° C).
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