[Top] [All Lists]

Re: SU carb

To: "Gary A. Graham" <>
Subject: Re: SU carb
From: Graham McCann <>
Date: Mon, 03 Nov 1997 08:29:59 +1100
At 10:59 pm 1/11/97 -0500, Gary A. Graham wrote:
>I read somewhere that one should solder the spring loaded plate
>valve in the throttle disc in the closed position. Should I do this?
>74 3/8 MGB


This is done when the springs under the valves on the butterfly become weak
and stay open when the throttle is closed thus making it impossible to get
the idle speeds down.

The valves are designed to lag decleration of the engine and so ensure less
unburnt fuel is emitted out the exhaust.  They are fine when new but time
(and heat) reduce the strength of the spring and so allow air to pass
through even when the butterfly is closed and so maintain the engine running.

To seal them remove both carbies and place them air cleaner side down on a
bench.  The valves can be clearly seen and soldered closed.  Do not try any
Silastic or glue products as they will surely break away.

If you find it difficult you can remove the butterflies and solder them
away from the carbies.  Make sure they go back into the same carby they
came from.

Doing this will make engine tuning, especially idling, much easier as the
valves tend to remain further open when the engine is hot and may remain
almost closed when the engine is cold.

Hope this helps,

97 MGF

Graham McCann  Rivett, ACT. Australia
Phone/Fax: +61 2 62889055

<Prev in Thread] Current Thread [Next in Thread>