Hi,
Looking for information reqarding exhaust valves. It appears to us that a previous owner ground the valve seat too much such that the exhaust valves are too far in. Need to know if a; this is normal b; are oversize exhaust valves available c; would it be possible to machine the intake valves down a bit?

The NHT exhaust seat have a very close ID to the small ID of the valve area.
I had a "shop" butcher my seats by cutting the ID. To correct it, the valve would have been so sunken it was rediculous....
I ended up changing the seats myself, buying $2700 snap-on valve equipment and I've never looked back. Been doing all my own work since then... including my Lotus car work(bare head alone is close to $3k).
Getting good work on a norton does require luck or a shop that really knows norton, not just a british (BSA/triumph) shop.