Randall Young wrote:
>
> Larry :
>
> I would start by disconnecting the vacuum line(s) to the dizzy, and trying
> to get it to run that way. I'm not certain (and my Haynes is unclear on the
> subject), but I think a 72 US-emissions model would have only vacuum retard
> anyway.
>
> With it disconnected, the ignition timing should move smartly (no visible
> delay) to match engine speed. If it doesn't, then the dizzy (or the
> mechanical advance mechanism inside it) needs attention.
Just to add one quick note to explain to Larry about the vacuum retard.
If you look carefully at the vacuum port on the carburetor, you can see
by its location that the port is uncovered as the throttle plate comes
off the idle position, and therefore loses vacuum after idle. Bringing
engine rpm above idle should show a slight jump in advance. If there is
none, and the advance is also slow to come back on deceleration, there
are a couple of possibilities.
If you pull the vacuum line to the solenoid and plug it, as Randall
suggests, and the advance/retard of timing is crisper, then this
suggests a problem with either the vacuum solenoid sticking, or that
there's a restriction in the thermo switch (this to me seems much more
likely--the thermo switches are not life-of-the-car items--and it's very
possible that the switch is stuck in the nearly closed position).
You can check the switch, first, by looking for vacuum at idle after the
switch, when it's cold and then when hot.
If it's opening and closing properly, the line between switch and vacuum
solenoid should lose vacuum promptly when vacuum is lost at the carb
port.
If there's no change in advance/retard behavior with the vacuum line to
the solenoid disconnected and plugged, it's very likely that the advance
plate is sticking. I have been able to fix this problem in the past
without completely disassembling the distributor by heating fresh engine
oil in a pan (this can be done safely on any warmer with closed coils,
such as a coffee maker), then dunking the distributor (after removing
the vacuum solenoid, points and condenser) in the oil, head first, and
letting it sit for several hours.
Then drain it thoroughly for another hour or two, then wipe the inside
clean of remaining oil and replace the solenoid, points and condenser.
That, very often, will do the trick.
Cheers.
--
Michael D. Porter
Roswell, NM (yes, _that_ Roswell)
[mailto:mporter@zianet.com]
The gulf between content and substance continues to widen....
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