John,
A little light ticking from the valves is quite normal. If it is at all loud,
and particularly if you can hear it clearly when driving, then all is not as
it should be.
Never fear, there is a 95% chance you just haven't got your valve clearances
adjusted correctly. By design, there is a small gap between the rocker and
the top of the valve. This gap is there to ensure that the valves close fully
when they are supposed to be closed, rather than being held very slightly open
by the cam. The slight ticking you should be able to hear all the time is
this gap being taken up as each valve starts to open.
It is easy to adjust this gap. Remove the rocker cover (may be worthwhile
buying a new gasket in advance for when you re-fit it - they are dirt cheap).
The gap is adjusted by loosening the lock-nut on the threaded bit at the end
of the rocker arm, then screwing the threaded bit down until you can just slip
a 15 thou feeler gauge between the rocker and the valve tip. Re-tighten the
lock nut, holding the thread in place to make sure the gap doesn't change as
you are tightening up.
This (the standard) process does have a draw-back, as it doesn't allow for the
fact that the valve might have worn a hollow in the rocker end. Bad ASCII
art:
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The feeler gauge will not account for the depth of this hollow, so you will end
up with an effective gap of 15 thou plus the hollow depth. The ideal way to
get the exact gap (so I have been told) is to adjust the threaded bit until it
just contacts the valve tip, then back off by ? degrees. This will give you
the exact gap. However, I can't remember how many ? degrees is, as it is
dependant on the thread pitch, which I can't remember. Anyone out there know?
Say the pitch is 50 thou, then the angle to back the thread off by will be
360*15/50=108 degrees - hard to do exactly, but a quarter turn plus a little
should be close enough. You get the idea.
As for the oil light coming on under heavy braking (or cornering), this is
usually a sign that you have let the oil level get MUCH too low - most of the
time the feed to the oil pump is submerged, but under heavy loads all the oil
in the sump gets thrown to one side or end, and the oil pump feed can suck
nothing but air - so pressure drops until the pump is pumping oil again. If
you are fully topped up with oil, there is something sinister afoot, and I'm
not sure what it can be.
Richard & Daffy
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