James--- If your vacuum supply is constant and the timing won't stay
retarded, (14 deg. would be about right) then the retard capsule may be
leaking. Tee in a vacuum gauge to the test line to see if you are
getting enough vacuum to pull the points plate CCW. Standard manifold
vacuum of 20 inches would be plenty, but even 10 inches should work.
A properly working ignition retard at idle, has little effect on
performance, since the retard is canceled as soon as you dip into the
throttle. It is there for emission pruposes. (NOx reduction)
You are correct in that the ports on the SU is not there for vacuum
retard, but rather for vacuum advance. The port for vacuum retard on the
1973 model ZS is under the bottom of the rear carburetor.
Dick
From:
james.f.juhas@snet.net(James Juhas)
I'm trying to tell whether the vacuum retard unit on my 1973 TR6
distributor is working properly. When I apply a vacuum to it, it moves
but does not hold the vacuum, so returns to its resting position. It's
as if a sudden vacuum signal would move it, but then it drops back.
Should it behave this way, or is it simply leaking?
A supplementary question is: does this engine really need this feature
for performance reasons,
or is the vacuum retard only an accommodation to emissions control?
I am converting this car from downdraft webers to SUs and this provides
me with a vacuum signal at the carb which, I believe, will be present at
partial and full throttle, and this seems wrong to me to connect this to
a retard unit. In the normal Stomberg setup, where does the retard
vacuum unit port attach?
Thanks.
|