Tim,
What are the climatic conditions where you are? My experience is that the
Z-S carb temperature compensator valves don't really handle very large
underhood temperature changes. For example, once upon a time I tuned a
stock 1971 TR6 with freshly rebuilt adjustable needle carbs in the
summertime in Phoenix (100+ degrees) and had it running really smooth at
idle. To my surprise, when I drove the car to northern California and
encountered 50-60 degree foggy weather it ran noticably leaner and needed
richening up to get its performance back. I know that you have just
installed a new header on your car, so is it possible that the header
coupled with hot summer weather has significantly raised your underhood
temp? My experience is that the idle trimmer screws don't change the
mixture enough to compensate for major temperature changes, as they were
designed just to bleed a little more air in to the mixture to pass smog
tests. I believe that you will have to adjust the needles. Keep us
informed, Tim.
Rex Townsend
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