The purpose of these valves is to help the engine run better
and cleaner when it is in an overrun condition,
i.e. when the car is making the engine go, instead of the
other way around.
They should have no effect at idle or when your foot is on the gas.
They do obstruct the throttle passage a bit, so completely
removing them should theoretically give you a little bit more top-end
performance.
Doug Braun
'72 Spit
At 04:06 AM 8/21/01 , T. .R. Dafforn wrote:
>Hi Mike,
>Sophie has her overrun valves soldered up, and as you saw a few months ago,
>there seems to be little change in her speed. I have to say that I have not run
>a spit with the valves working, so I have nothing to compare with.
>However I had a look through my trusty SU manual and they only mention that the
>valves are solely there for improved economy.
>One thing I would say though is that it is probably better to replace the
>butterfly with new ones without the valve (they are not that expensive), and
>the
>valve does a good job of blocking airflow at full throttle. It is also easier
>to
>replace the butterflies rather than trying to solder them in situ.
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