Thanks for your comments Chaps!
I've decided to cool the engine using the top up solution.
Also, to dry out by piping air through, from an aquarium pump, for a couple of days afterwards.....
Looks as though the weather has closed me down again.....
Only got a little bit done.
The top deck casting was machined barrel shaped, both sides!
Drawfiled/ emeried .005", from the centre of this side......
And .025" or so, from this side......
Emeried out the rust, from the casting airway bore.....
Fitted the 5/16" tube......
Remembered to overlap the joint face area.
So it will butt against the new section of displacer housing, when I mill the new joint face ring.....
Also, roughed out a new 3mm thick cover plate.......
It's snowing like Billy Ho at the moment. Guess it will be some time before any more work gets done.....
David D