Fw: [xj-s] Re: Valve lapping

["Richard Chapman" <richardc@sanderson.co.nz>]

>Kirby wrote:
>>I have always presumed that lapping valves would make them shiny, but
>>it appears to leave them with a grey matte finish.  Is this normal,
>>or am I doing something wrong?
>
>Normal
>
A handy hint I heard years ago from a very old mechanic (Yoda)....

When you thnk the valve is lapped fully, clean off ALL the paste from the
valve and seat. Then briefly lap the valve dry in the seat. You should see a
very thin shiney line around the valve head and seat, exactly where contact
is occurring. This line should be unbroken, indicating total sealing. Use a
magnifying glass or loupe if you need. Most important is that the line is
unbroken, no matter now thin it is, it will soon hammer out with engine
operation. Continue to lap as normal and retest until perfection is
achieved.

When I first used this technique, I found small gaps despite the fact that
the whole seating area was matt grey as it should be. Any gaps will cause
leakage and seat burning. I've compared this method to the engineer's blue
method and it seems to give better results IMHO.

This one ranks up there with pre lubing bearings on engine assembly,
offsettetting ring gaps 180 deg, etc. WIWIG (worth it's weight in gold - hey
did I just invent an acronym?!?)  Once again IMHO.

Richard XJS-HE '83 (Steam powered - in bits)

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