Dick (and Stan):
Thanks. I can't test in place because of where my vacuum supply is.
I'm checking with a vacuum pump, and it appears to leak. In any event,
I can't use a retard mechanism anyway with the SU setup. I'd love to
acquire a vacuum advance distributor or get to full advance solely on
the mechanical advance. Perhaps my Bently manual will tell me what
advance should be at various RPM?
Jim
Sally or Dick Taylor wrote:
>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.
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