> Also, while on the subject of Webers, which direction should you turn the
> idle adjustment screws to lower the idle speed? My car idles at about
> 1000-1200 rpm when you come up to a stop after driving, than after a few
> seconds, the idle drops to about 700 rpm and stumbles somewhat. My theory
> is the idle is too high and after a few seconds, the plugs of two of the
> cylinders get fouled so the idle drops down and it runs on only two cylinders.
> What do you think?
I think that there is a transition between "normal" and "idle" operation
that takes a few seconds. The idle needs to be fixed, but the drop in rpm
after a few seconds that you are seeing is normal. As to which direction to
turn the screw, it depends on which screw you mean - there is a throttle-stop
screw and an idle-mix screw, both of which need to be set correctly, and of
course they are not independent so you have to futz around a few times. The
throttle-stop screw is fairly direct - clockwise to increase, anti-clockwise
to reduce idle rpm. The idle-mix screw is more complex - the effect it has
depends on which part of the mix curve you are at. Try backing it out a bit,
then setting the throttle-stop to get about 850-900 rpm. Then slowly tighten
the mix screw (clockwise) until the engine starts to stumble. Back off the
mix screw a bit, then set the throttle stop to the right idle speed, then
repeat the cycle until bored or happy.
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John R. Lupien
lupienj@hpwarq.hp.com
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