I have one on order. I'll do a photo shoot of the lathe setup and the groove-cutting procedure soon. The valve I listed is not a standard BBC exhaust valve, and it has a 45 degree face angle instead of the 30 degree angle used on the stovebolt valve. It would probably be simpler to change the seat angle of the stovebolt head instead of trying to modify the valve face. That 30 degree angle was another one of those "over-engineered" features of stovebolts- - - -not really necessary for practical use.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!