I have been helping the following person with some ZS carb questions but he
has now taken the discussion to an area that I am not familiar with as I
have a '70 TR6 and do not have the same ignition set up as he is describing.
If you can offer an thoughts, I will pass them along and suggest joining the
list as a great resource. Thanks.
Scott Suhring
Mechanicsburg, PA
'70 TR6
'59 TR3
Scott,
Thank you very much for the information.
I have been driving the car and have adjusted the carbs and they seem good.
However, the problem persists and I keep returning to the ignition,
specifically timing. The car continues to have an intermittent skip at
highway speeds. The problem will occur during all conditions at speed. I
know the carbs are your specialty, but the specifics I am questioning are
the vacuum lines from the carbs and the vacuum retard in relation to the
timing. Being a 74, I have the thermostatic switch. To date, I can find
nothing explaining the function and purpose of this device. It would appear
that it is intended to change the vacuum conditions between hot and cold
operation. I have kept the vacuum lines the way they were when I purchased
the car. The vacuum retard unit is an open connection to the two vacuum
connections adjacent to the bypass valves on each carb when the thermostatic
switch when cold. The vacuum line that comes off the bottom of the front
carb manifold to the intake manifold is a closed connection when cold. The
fourth connection on the thermostatic switch is plugged. I have not yet
determined what they do when the thermostatic switch is hot, but prior to
investigating this, could you possibly explain what the thermostatic
"switch" is supposed to do when hot? The car has always seemed under-powered
and I have properly checked and rechecked the timing, but this is done with
the vacuum retard disconnected. Admittedly, the vacuum retard unit is one
component that I have not replaced as it seemed to be operating properly,
but I am now very curious as to whether the vacuum lines on the thermostatic
switch were ever correct. With no reference or specific diagrams on the
connections, I have no way of determining if what exists is correct. The 74
vacuum lines and thermostatic switch are a bit of an enigma and nothing
seems to exists on how this was designed to function. Having looked into
everything else, I am suspicious since the problem could be symptomatic of
retarded timing and the vacuum is directly related. I know that my Nortons
run very similarly when the timing is too far retarded.
If you could provide any guidance or assistance, it would be extremely
appreciated!
Thanks
Turk
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