VALVE
- WORN
Valve
stem wear is a normal occurrence after many thousands of miles are clocked
up on an engine.
The premature
appearance of severe stem wear and guide wear is abnormal. There are many
causes of this condition and care must be taken to ensure the cause is eliminated
at the time of guide and valve replacement.
- Insufficient
guide clearance after a cylinder head overhaul can cause the valve stem to momentarily
seize up and subsequently create aggressive wear in the guide or stem.
- Bad
guide to seat alignment
will accelerate stem and guide wear as extra side thrust is placed on the
head of the valve as it attempts to square up onto the seat.
-
Incorrect rocker arm geometry
will exert abnormal side thrust on the tip of the valve causing abnormal
stem and guide wear.
- Lack
of stem lubrication
is another cause and should be checked upon reassembly. There are many different
methods used to ensure oil finds its way to the valve guides. Most times
a small oil drilling or spray bar is used to lubricate the rocker assembly
and valve guides. Check operation of oil system after assembly.
- Dry
assembly
and dry start can cause the initial damage that accelerates the stem wear.
Use good quality, clean engine oil to saturate the guide and stems upon
assembly.
- Not
polishing valve stems
after unprotected bead blasting of valves will cause accelerated guide and
stem wear.
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can be excepted for errors, omissions or misuse of this information and procedures. The
information available on this site is for your instruction only and cannot be copied for
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UMR Engines www.engineproblem.com.au
