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<p>"... The vacuum advance/retard, if fitted, is only in operation
at low load."</p>
<p>This is something I've wondered about. This is true for
'manifold' vacuum, but the vacuum pickup off a Healey's SU carbs
is near the throttle, which I believe is called 'port' vacuum. If
my knowledge of Bournelli is correct, this vacuum is created by
air moving over the port, and increases with airflow.</p>
<p>Please advise.</p>
<p>Bob<br>
</p>
<br>
<div class="moz-cite-prefix">On 2/12/2017 9:15 AM, Oudesluys wrote:<br>
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<div class="moz-cite-prefix">Not quite, setting the static timing
was the only means at the time and the instructions should be
accurate. Nowadays it is more convenient to set the timing
dynamically, but without vacuum and at stationary revs, which is
in most cases the same as the static timing. The so called fine
tuning is in practice irrelevant except when the car is tuned on
a rolling road. However you can check if the centrifugal advance
mechanism is working properly by keeping the engine on e.g. 2500
or 3000rpm and check what advance is indicated. Disconnect the
vacuum line for this though. The vacuum advance/retard, if
fitted, is only in operation at low load. <br>
Kees Oudesluijs<br>
<br>
<br>
<br>
Op 12-2-2017 om 12:51 schreef Simon Lachlan:<br>
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<p class="MsoNormal"><span>In this instance, static timing
would precede dynamic timing because the car was so far
out of tune that the engine would not run.</span></p>
<p class="MsoNormal"><span>In my thinking, static is only used
to get the timing onto the right map page, enabling the
engine to be started and then tuned more precisely by
other means.</span></p>
<p class="MsoNormal"><span>Simon</span></p>
<br>
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