Dear all,
Having been away for a couple of days and finding a mass of communications on
the subject of oil, I thought I'd
throw in my dollar's worth of perceived wisdom (I don't have 2 cents but I've
got a picture of dear old George
stuck to the wall here).
Firstly a bit of background:
The first part of the system fed by the oil pump is the crankshaft, so this
receives the maximum delivery pressure.
As the main and big-end bearings wear, the pressure will drop off somewhat,
especially as the oil warms up.
The pump will also wear gradually which compounds the problem.
The six cylinder engine has a cartridge oil filter with no anti-drain
properties so, on switching off the engine, all
the oil drains back into the sump. When you re-start the engine a few hours
later, the oil has to be pumped up
again into the filter and then into the bearings. The knocking noise on
startup becomes more prominent on older
engines due to the play in the bearings, but you will notice that it normally
stops at more or less the same instant
as the oil light goes out. ( This, I assume, shows that the oil pressure switch
is connected in on the feed between
the filter and the crankshaft.)
Now, in my view, if there is no further knocking once the pressure has built up
and the light has gone out, then
your engine is fine - if it continues to knock then it's time for some serious
work to be done. Some owners have
different techniques for minimising the problem. One is to turn the engine on
the starter, without using the
choke, until the oil light is extinguished. Because the engine doesn't fire,
the cranking speed is kept low enough
that the lack of oil can do little damage. As soon as the light goes out, they
pull out the choke and they're away.
The method I use is to start the engine normally but push the choke back in so
that the revs don't get much
above normal idling speed. The important thing is not to touch the throttle
until the light goes out and the
knocking stops. This should only take about 2 or 3 seconds.
The spin-on adaptors available for six-pot engines do work. They employ the
disposable canister type of filter
which is supposed to have an anti-drain valve built in. Tests have shown that
these valves are frequently less
than ideal, some working much better than others. However, if you ensure that
the filter hangs downwards (i.e.
mounting face upwards, but not necessarily vertical) then less reliance is put
on the anti-drain valve and good
reliable old gravity comes to your aid.
If you are going to fit one of these and you have been considering an oil
cooler also, these should be done at the
same time since the filter adaptor will be supplied with the oil cooler
connections.
Most four cylinder engines have anti-drain canister oil filters but, because of
the problems mentioned, these do
still exhibit oil drain-back. A couple of inventive TSSC members have made
adaptor plates to go between the
block and the filter so that a maximum of about half the oil will still remain
behind.
Now to the rocker feed pipes kits. These take oil from the point where it is
at maximum pressure (at the pressure
switch) and deliver it directly to the rockers via the plugged hole at the back
of the head. While obviously
benefitting the rocker shaft, it has been suggested that they should not be
fitted to engines that have a lot of
general wear since oil is taken away from where it is needed most and the
pressure at the crankshaft falls further
than is desirable. The person who observed a pressure drop (recent email)
illustrates this quite effectively. I
remember a correspondent to Practical Classics magazine saying that when these
feeds were first introduced
many years ago by a different company, a restrictor was included to ensure that
the oil bleed off was kept under
control because a badly worn rocker shaft would present a low resistance path
to the oil and could take a
catastrophic amount of oil away from the crank. However, it appears that the
feed kits currently available do not
have a restrictor and so their use should be properly and carefully considered.
At the very minimum, perhaps
the rocker shaft should be replaced if it is bady worn. Otherwise, at best you
are just masking the problem by
improving the oil feed (and fitting a cast rocker cover ) to deaden the noise.
At worst, you take too much oil
away from the bottom end and !!!!
Any comments, flak etc.?
Phil
From: Phil Willson
13/60 Register Secretary
Triumph Sports Six Club
Tel +44 (0)171 975 5338
Fax +44 (0)181 981 0259
email p.j.willson@qmw.ac.uk
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