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On the cylinder head, are fitted intake and exhaust valve, valve seat, valve guide (pipe), valve
spring, valve rocker and support.
The cylinder head is secured onto the engine body by bolts. When securing the bolts, it is
necessary to use a torque wrench, to tighten them one by one, by several times, as per the
sequence shown in Fig.2. At first, pre-tighten them; then tighten them as per specified
tightening-torque values. In case of assembly/disassembly of the cylinder head, after the engine
runs heat at first time, stop and cool the engine, and re-tighten the bolts as per specified
tightening-torque values, and re-adjust valve lash or clearance.
Fig. 2 Tightening sequence of bolts on cylinder head
On the upper part of the cylinder head, is placed the fuel injector, forming an inclination
angle with the centerline of the cylinder head. In the mounting hole of the injector, there is a
copper shim, used for adjustment of the height from the protruding injector to the base plane of
cylinder head, and used for sealing. When installing the fuel injector, please evenly and tightly
press the pressboard, without any leakage. It is important that when installing the pressboard, the
side with an inclination should face downwards.
1. Intake and exhaust valve, valve seat and valve guide
Both intake and exhaust valve and valve seat should all be paired ground, to avoid leakage.
When on the sealing surface between valve and valve seat, there is burning, pits or wear-off,
causing leakage, it is necessary to grind them. Apply some grinding paste (fine valve sand) on the
conic sealing surface of valve, then pair-grind the valve and valve seat, until a uniform, continuous
and gloss-less sealing surface is obtained. Grinding paste is strictly forbidden to enter the valve
guide. After the grinding, valve, valve seat and valve guide should all be carefully cleaned,
Chapter IV Structure
I. Cylinder head
18
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