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RE: Vacuum lines

Subject: RE: Vacuum lines
From: "Sluis, John" <>
Date: Wed, 03 Apr 96 08:07:00 CST
This gizmo is a transmission controlled switch.  To minimize emissions, BL 
decided to only allow the distributor vacuum advance to work at road speed.  
As a result, this box is installed.  The wiring is a circuit that energizes 
when the gearbox is in 4th gear.  That opens the vacuum circuit to the 
distributor to allow the advance to function.  There should be one vacuum 
line coming from the manifold and the other routes to the advance diaphram 
on the distributor.
To: mgs
Subject: Vacuum lines
Date: Tuesday, April 2, 1996 3:16

I have a 78B which is pretty much stock.  On the metal pedal box located
between the brake master cylinder and clutch master cylinder, there is
what I think is a vacuum switch.  There are two wires coming from the
bottom and two places for hoses to attach --- only there aren't any
hoses there.  I can't find any reference to this in my Haynes manual or
the Moss/VB catalogs.  What is supposed to be connected and what does
this switch do?

Thx...Andy Slupecki
        78 MGB (in more pieces than I would like with spring

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