Chris
I checked on my car, a standard 3000 mk2 with three HS4 carbs, and there
is very little vacuum at idle, and when I give it some throttle it seems
the vacuum goes away. As I recall, vacuum has been stronger on other
cars I have checked.
You say that these vacuums are opposites of each other, I fail to
understand this. Can you elaborate this a little, please.
As I understand it we need some ignition advance at idle, because the
mix is weak and takes a long time to burn, this is accomplished with the
vacuum advance. And we need a some advance at high revs because the
pistons travel very fast and the spark must ignite the load some time
(degrees) before TDC to make useful work, this is accomplished with the
weights and springs. What we don't need is ignition advance at low
engine speed and open throttle, because that will cause detonation and
nasty things will eventually happen.
As the vacuum in my car is quite weak I wonder if the Healey distributor
vacuum thing is more sensitive than on "normal" cars?
Best regards, Per in Sweden
Chris Dimmock skrev 2012-04-16 18:18:
Fair call John.
A Lucas healey distributor uses ported vacuum. Which is an SU thing. Vacuum is
taken at the throttle plate. Not the inlet manifold.
These - ported vacuum and manifold vacuum - are exact opposite vacuums.
Opposite.
That's why you never connect a std Healey Lucas distributor vacuum advance to
a manifold vacuum port on eg a triple weber Healey.
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