Jim...
You've got emissions carbs on your '68
along with an emissions ignition curve
(distributor). Is your distributors vacuum
line hooked up to a carb or to the intake
manifold? Is all the other emissions equipment hooked up, operable and
operating??
The carbs have a spring-loaded needle
within. This "rests" against the inside of
the jet and "wears" itself accordingly,
upsetting the factory mixture ratio over
time, normally leading to richness, all
else being equal. But it is leaness that
normally leads to "off idle" stumble, unless it's really rich to the
extent you
can see black smoke out the exhaust
under these circumstances.
"Leaness" on acceleration can be caused
by a number of different things but basically, too much advance or too
little
fuel as the pedal is "pushed" is the culprit.
Oil within the dashpot serves as the
acceleration "jet" or "circuit" in the SU.
The heavier the oil, the more slowly the
air valve lifts under demand...the slower,
the "richer" the mixture goes on acceleration. So, whatever weight oil
you
are using in the dashpots....go a bit
heavier for a "richer" air/fuel ratio OR....as you've pointed
out...(and this is
my bet).....
the timing could be a little more advanced
than it should be. Or, distributor vacuum line leaking? Vac. cannister
on distributor
working? Hooked up within dizzy (spring
has a way of separating from the "peg"
within...don't ask me how:)?
Cap'n. Bob
'60 :{)
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