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For those of you who would like to know what I do to replace a combustion chamber read on!

Firstly I heat the head (I use gas mark 9 ;-) ) so that I can remove the old chamber from its shrink fit of 3 to 4 thou.
When it's hot enough I push back the valve guides and drift out the used chamber. I then turn a billet of ca 104 alloy bronze (pic 1) to fit the existing recess in the head (pic 2) which is basically the shape of a top hat.
After turning the new billet piece to size the head is reheated and the new insert put in place, this is a tricky manoeuvre as you must not get the billet askew or you are in it (the brown stuff) get it wrong and you start again!

Once the head has cooled down to where I can just about get hold of it without discomfort, I then reseat the new insert, because when the head cools, it moves away from the inserted billet (let it cool to far and you wont move it).
If it's not reseated it will move when you run the motor which is, of course, a No No!

Now we can start making pretty swarf (chips to uncle sam). First drill the holes for the plugs - 2 per cylinder in this case (pic 3), it's easy to drill a flat surface now, but, as you will see, not practical later on in the job. Now the head must be at the valve angle for the next op which is to cut the pentroof part of the chamber (pic 4 & 5).

This is painstaking work but the result is worth it!

- Brian

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