>In the case of the post 1974 TR6s (TRF vol 1, page 100), there are even
>more vacuum lines from the valve. They connect to the top of the carbs; I
>have no idea what they do.
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I am not familiar enough with this arrangement on the TR6, but it is
typical of other vehicles and I'll use it to illustrate the effect-
This IS to prevent run-on. Vacuum is applied to the top of the fuel bowl,
when the engine is shut off, to prevent fuel from entering the carb throat.
If you were to block the vent in the float chamber the fuel will not be
able to be drawn into the combustion chamber to be burned when sufficient
"vacuum" is created to over come the Venturi effect in the carb. Venting
the bowl to the engine instantly creates enough vacuum to do this. The idea
is, if no fuel is allowed to enter the carb throat, then it cannot be
sucked into the combustion chamber. If there is no fuel in the combustion
chamber, then it cannot be burned - Since run-on is caused by the burning
of fuel from hot spots in the combustion chamber, the result *should*, and
if operating correctly, be no run-on.
Barry Schwartz (San Diego) bschwart@pacbell.net
72 V6 Spitfire (daily driver)
70 GT6+ (when I don't drive the Spit)
70 Spitfire (long term project)
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