[Roadsters] Vacuum Advance Issue?

[Keith0alan at aol.com]

The vacuum advance is shot but that is not the source of your stumble. That 
 is the classic symptom of being a little lean. Richen up your carbs a 
little. If  you have SUs then about a quarter to half turn on the mixture knob 
on the  bottom. If Solex then one step smaller air or one step bigger main. 
Try the air  first.
 
The vacuum advance has been around a lot longer than emission concerns. It  
is a performance item and the car will run better with it working. 
 
keithw
 
 
In a message dated 6/12/2013 8:11:22 P.M. Pacific Daylight Time,  
graemes at internode.on.net writes:

First up, the vacuum advance is an emissions device. 

You can safely
remove theB vacuum source and test drive the car.  

It only does its thing on
cruise or trailing  throttle, it does not
contribute to engine power. 

The
only caveat is you must BLOCK OFF the vacuum hose to prevent  the
engine from
sucking in air when the vacuum port is exposed in  the
carb. throttle. 

For
sure the vacuum advance  mechanism in the distributor does
eventually gum up so
badly it is no  longer operative. 

Providing the plates inside the  mechanism
are not pitted and
groovedB by the tiny ball bearings, it  should be reasonably
easy to
clean and re-lube so it all functions  smoothly. 

The vacuum actuator
is a different kettle  of fish. 

If the arm doesn't operate when subjected  to
vacuum it is schtuffed,
non-repairable. 

Once  the diaphragm is holed or
perished, game over. 

Suction by the human should be enough but a little
vacuum pump is
handy  to see that things do operate correctly and more
importantly,
stay  operated. 

i.e. with a constant source of vacuum,  the
mechanism should stay
put,B not slowly return to normal, that  indicates a
vacuum leak
somewhere.

Let me know if  you need any pics. and I'll email them
to you
directly. 

Regards,  Graeme S. 

----- Original Message -----
From:
"wattaj"  @yahoo.com> 
To:"Roadster List" 
Cc: 
Sent:Wed, 12 Jun 2013  19:45:58
-0700 (PDT)
Subject:[Roadsters] Vacuum Advance  Issue?

Hello,

I have an
issue where at a steady highway  cruise speed, just around
3000 RPM or higher,
I get regular hiccups,  sputtering, etc.. If I
drop below
3000 RPM I am
usually fine. The  engine will pull strong all the way
up to
where I dare
accelerate. I  have always been suspicious of my
distributors
vacuum  advance.
Popping of the distributor cap, I tried to manually
move  the
advance it by
sucking on the tube, but it would not budge. I took  the
advance
mechanism off
the distributor and it was frozen stiff.  After some
serious
pushing I got it
to move manually, but would still  not move under
suction. It
looks like I
should replace the vacuum  advance unit. I am curious if
that
might be the
cause of my cruise  speed issues? Thanks in advance (no
pun
intended) for  the
help.

Cheers,

Alan
Tualatin,  OR
67-1600
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