Slightly off topic, but when I eventually get around to rebuilding my Sunbeam S8 motorbike, I will need to have harder valve seats installed to cope with unleaded petrol - unless anyone has experience of the lead supplement that I hear you can get for the petrol?
Or maybe there is a petrochemical expert in the forum who can tell me how to treat the petrol to be like leaded?
If the head is aluminium, then it must have hardened valve seats. These will be good enough for unleaded fuel. A good solvent cleaner will show the edges if you have doubts. Simple.
If it's cast iron, then it
might be good enough. I put 50,000 miles on a Pinto without hardened seats without a problem. 4,000 miles on a Cologne V6 created such valve seat recession that it barely ran. Neither case is unusual. Lead replacement additives are still available, and considering that you're unlikely to do more than a few thousand miles on an old motorbike(for the rest of your life
) will be all you need.