Mike:
My rough running was due to misadjusted bypass valves. These
should be closed at
idle, but mine were open. 1-1/2 turns CCW on each and life was MUCH
better. These are
vacuum "leaks", but I could not find them because they draw air from the
inlet of the
carburetor. So if you have checked for leaks everywhere else, check your
bypass valves.
If your vacuum retard is not working, then you want to use the
static timing
(10 or 12 BTDC, depending on year) no matter what. You only use the
dynamic timing
if your vacuum retard is working (4 ATDC) and connected, and your engine
is fully
warmed up so that the thermal vacuum switch is open. Then when you
disconnect the
vacuum retard, the timing advances to the static value and the idle
speeds up.
Wiggling the unit simply shows that the unit is mechanically
connected, because
it moves the points back a forth a bit as you wiggle it. When you
disconnect the
vacuum line, is there vacuum present in the line? If yes, your vacuum
unit is bad
(mine is leaking, you can hear it hiss when you apply a vacuum, and it
will not
hold vacuum for more than a second or so). If there is no vacuum
present,
1. Your engine is not fully warmed up, or
2. Your thermal vacuum switch is bad, or
3. The vacuum line is plugged, or
4. Your vacuum lines are misrouted.
Cheers,
Vance
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of DaCRANEz@aol.com
Sent: Monday, May 03, 2004 1:54 PM
To: 6pack@autox.team.net
Subject: vacuum retard
Vance touched on something that I have been wondering about. I have
been
having problems with my newly rebuilt engine running roughly. I finally
got the
timing straightened out but it runs like it has a big vacuum leak.
Believe me
I have checked everything-isolated carbon canister, checked throttle
shafts,
new hose to servo,retightened manifolds. Vance mentioned that the
engine
should pick up revs when vacuum line is detached. Mine doesn't. I can
wiggle the
vacuum unit and it will speed up or slow down engine speed. Is this
where my
problem in whole or in part lies? I hate to buy a new vacuum unit
(68.95 @
VB) if it is not the problem. I considered buying a rebuilt distributor
but
after the layout for the rebuild I have to lighten up a bit on spending
or I
won't have any gas money. I almost forgot-whether I have the vacuum
hooked up or
plugged off does not affect dynamic timing.
Mike C '71 CC62976L
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