Terry,
Thanks for starting the thread!
The thermal vacuum switch that you refer to actually shuts-off the
vacuum retard for the benefit of emissions, (when the engine is at
operating temperature). The engine will not overheat due to the ignition
timing being retarded, (actually the reverse is normal).
Best regards,
Jim Swarthout
Gary,
If you have the vacuum retard connected, you time the engine at 4 ATDC.
If
you have the vacuum retard disconnected, you can time the engine @ 8-10
BTDC. I have the vacuum retard disconnected on my car and I time the
engine
at 10 degrees BTDC.
The vacuum retard is for emissions purposes. The engine timing is
retarded
on your car to reduce the emissions output at idle. As soon as you step
on
the throttle, vacuum is dropped to the retard and the engine runs
normally.
There also should be a thermal switch in the top radiator hose that
controls
this function. Triumph engineers found the engine would overheat after
prolonged idling when the timing was retarded so they included the
thermal
switch to drop the vacuum to the retard if the engine became too warm.
If
you're missing the thermal switch then you're best bet is to disconnect
the
vacuum retard and time the car at 8-10 BTDC.
Hope this helps,
Terry Geiger
'74 TR6 daily driver
Florence, Alabama USA
http://www.ShoalsBritishCars.org/
> Just got my new motor running and what the manual is telling me is a
bit
> conflicting. I have a slightly modified 74 motor with all emission
gear
> removed. The manual is showing 4 degrees A.T.D.C., which goes against
> anything I ever heard. It seems to like it around 8-10 degrees
B.T.D.C.,
but
> I haven't started tuning the carbs yet so not sure about actual
running
> circumstances (on the road). Can anyone fill me in on what they have
done
in
> similar circumstances?
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