Inspecting And Repairing Cylinder Head And Valve Mechanism; Measuring Distortion Of The Bottom Surface Of The Cylinder Head; Measuring Clearance Between Rocker Arm And Rocker Shaft; Measuring Perpendicularity And Free Length Of Valve Spring - Mitsubishi Heavy Industries SL Series Service Manual

INSPECTION AND REPAIR OF BASIC ENGINE

1. Inspecting and repairing cylinder head and valve mechanism

1.1 Measuring distortion of the bottom surface
of the cylinder head
Refacing of cylinder head should be kept to an abso-
lute minimum.
Excessive grinding of the cylinder head may result in
defects such as defective combustion and stamping
(contact between piston and valve).
With a straight edge placed on the bottom face of the
cylinder head, measure the bottom face distortion using a
feeler gauge. If the measurement exceeds the limit, grind the
bottom face using a surface grinder.
Item
Bottom surface distortion
1.2 Measuring clearance between rocker arm
and rocker shaft
Measure the inside diameter of the rocker arm and outside
diameter of the rocker shaft.
Replace the rocker arm or rocker shaft if the clearance
exceeds the limit.
Item Nominal
Rocker arm ø 18.9 mm
inside diameter [0.744 in.]
Rocker shaft ø 18.9 mm
diameter [0.744 in.]
Clearance
between rocker -
arm and shaft
1.3 Measuring perpendicularity and free length
of valve spring
Measure the perpendicularity and free length of the valve
spring. If the limit is exceeded, replace the valve spring with
a new one.
Item Standard
Free length 47 mm [1.85 in.]
Squareness
Lf
39.0 mm [1.535 in.]/
Rest length 131 to 145 N
/load {13.3 to 14.7 kgf}
[29 to 32 lbf]
6-2
Standard Limit
0.05 mm 0.10 mm
[0.0020 in.] or less [0.0039 in.]
Standard Limit
18.910 to 18.930 mm
[0.7445 to 0.7453 in.]
18.880 to 18.898 mm
[0.7433 to 0.7440 in.]
0.012 to 0.050 mm 0.200 mm
[0.0005 to 0.0020 in.] [0.0079 in.]
Limit
46 mm
[1.81 in.]
= 2.0°or less
= 0.5 mm
= 0.2 [0.0079]
[0.020 in.]
or less
over entire
Lf = 47 mm
length
[1.85 in.]
30.1 mm [1.185 in.]/
279 to 309 N
{28.5 to 31.5 kgf}
[63 to 69 lbf]
Measuring distortion cylinder head bottom face
-
-
Measuring clearance between rocker arm
Spring perpendicularity (gap)
Free length
Measuring perpendicularity and free length of
-15%
Measuring points and directions
Measuring
directions
Measuring
points
Measuring
directions
and rocker shaft
valve spring