Weichai America Corp.
Revision: August 2019 79
14
APPENDIX B
Appendix B: Tolerance Clearance for Main Parts of Gas Engine (Reference value)
#
Items
Theoretical value (mm)
1
Main bearing clearance
0.05
～
0.11
2
Connecting rod bearing clearance
0.045
～
0.09
3
Crankshaft axial clearance
0.04
～
0.25
4
Connecting rod planar axial clearance
0.30
～
0.50
5
Clearance between the connecting rod small end bushing and
piston pin
0.03
～
0.08
6
Clearance between piston pin hole and piston pin
0.003
～
0.015
7
Clearance between valve stem and valve guide pipe
0.03
～
0.06
8
Piston ring’s gap in cold
state
The first (top) ring
0.35
～
0.55
The second ring
0.75
～
1.05
Oil ring
0.3
～
0.6
9
Piston ring end face gap in
cold state
The first (top) ring
The second ring
0.06
～
0.095
Oil ring
0.05
～
0.085
10
Plane values of valve bottom recess cylinder head
1.0
～
1.45
11
Plane values of cylinder liner top above the engine body
0.05
～
0.10
12
Camshaft axial clearance
0.10
～
0.29
13
Camshaft bearing clearance
0.04
～
0.08
14
Clearance between valve tappet and tappet hole
0.006
～
0.035
15
Plane clearance between the piston top and the cylinder head
bottom
0.88
～
1.11
16
Plane values of piston top above the engine block
0.25
～
0.57
17
Valve clearance (cold
state)
Intake
0.2
Exhaust
0.3
18
Clearance between rocker arm and rocker arm shaft
0.016
～
0.052
19
Gear backlash between timing gear and the intermediate gear
0.07
～
0.24
20
Clearance between positive and negative electrodes of the spark
plug
0.35±0.05
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