Heater Tap.

[Mike Wattam <MikeWattam@domain.elided>]

Hi John

As you say, the water valve is soldered to the heater matrix, so the whole
lot would need to be removed and re-worked.  However, there may be an
easier solution.

What actually seems to happen, is that the valve body distorts and shrinks,
trapping the rotating valve.  If you disconnect the lever and reverse it on
the rotating valve and refit it with the screw, it is often then possible
to turn and pull it out.  The lever is supposed to be located on the
rotating valve with a d-shaped slot and corresponding protrusion on the
rotating valve, but this can get obliterated and if so on yours, this makes
it even harder to get out (besides all the blood rushing to your head, the
blood rushing out of your cut fingers, and the neighbours thinking you are
barking mad with your head up the footwell and your legs in the air) - well
you did want a Stag.  

At one time Tony Hart in London was selling a small slide hammer to remove
this, you could try him if the former method does not work.

IMHO - Mike Wattam
Chairman - Triumph Stag Register