Niall's 2000 306 XS A.K.A Craig

[Niall]

Ive heard of this happening before on Dixons race car that used the same engine as this! The way they fixed it was by using liquid metal on the affected area and it worked well.

I was going to but there's not really any need. It doesn't go through to anywhere.
The headbolt threaded the hole so I might make a core plug to put in there if I can be bothered.