I am going to add my story here. After investigating an oil leak on the way home from the Annual Rally, turns out the Comet has exactly the same problem.
Seeing as Chris just did this on the Rapide, we thought it would be relatively straight forward, ha ! wrong.
This Comet head has had a hard life. How was this bike even running? One of the locking rings was glued in, the other disintegrated, the valves are toast.
The work needs an engineer, new guides, valves, re-cut the seats etc.
Trouble is, there is nobody that can do the job and get the head back in time for me to ride it before Summer's over. Unbelievable.
{ Wouldn't it be great if a rich person/company sponsored a Vincent apprentice scheme to get young or established engineers learning the speciality, knowing they had customers lined up waiting ? Perhaps it would create an interest in the Marque amongst young people? }
Anyway, Chris is going to do it himself. The oversize guide is 566", and I can order everything he needs.
Buying a valve cutter, learning how to use it and getting that angle right should be fun.
Photos of the metal flying around in the head, the damage and the valve which looks like it's been used for golf.