Stan---This subject comes up every now and then, and you may see
different responses. Here's mine:
The switch has one purpose, and that is to interrupt the vacuum retard
that goes to the distributor. This interruption only comes in when the
coolant temperature reaches about 200 deg.
The vacuum line that comes from a carburetor to the vacuum switch should
only originate from one source, that being a vacuum port on the engine
side of the throttle plate, (or butterfly). There should only be vacuum
present at this source when the throttle is closed, as that's the only
time we want ignition retard to occur.
This means we do NOT want to take vacuum from anywhere else on the
carburetor, or intake manifold. To do so would keep the ignition timing
retarded when it shouldn't be. (Poor performance and mileage)
So, if still in doubt, you can remove the vacuum retard line, plug the
source, and set the timing at idle to 10 or 12 deg. BTDC. With the
timing set to this spec, the engine would not be idling "retarded" and
have no effect on engine temperature.
Illustrations for your model year is shown in the TRF catalogue, listed
under Emission Controls.
Dick
Stan wrote:
One of the great things about eBay is the many pictures of TR6 engine
compartments spanning all years... I've noticed quite a range of model
years with and without these thermostatic vacuum switches in the top
hose and notice that none of them are configured like mine.. which
brings me to my question..
Since these are switches there must be one or more vacuum sources and
one or more vacuum targets. One of the sources seems to be the front
carb and on some cars one of the targets is the distributor retard. So
I'm basically confused about what problem this switch is trying to
solve, what are the designations on the switch, why are several of mine
blocked off, how should it be configured for a 74 and half TR6 anyway
and what are the consequences of just plain old removing it as I see in
many pictures, assuming I plug up the exposed holes on the carbs and
relocate the dizzy retard to some other vacuum source like the banjo on
the inlet manifold ?
Stan
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