I find those rebuilt engines quite fascinating. I've often felt that many so-called 'restorations' are more correctly regarded as replicas including original parts.
The amount of work and effort involved is enormous, really a labour of love.
I'd guessed the approximate meaning of the welsh signature from context. My translator was rendering some part of the first phrase as 'heartburn' for some reason, which rather confused the issue. Using translator software is a bit of a black art, sometimes...
I've worked in Wales off and on for a good few years, being in the oil and gas industry, so I'm 'functionally polyglot' to some extent along with several other languages, like quite a few people in that line of work.
I've never attempted to speak it, because I find that welsh speakers would rather speak english than have you speak welsh - it's a bit like japanese, that way.
The Japanese are convinced that no-one can speak japanese except them, and they have the habit of speaking japanese in front of you then replying in english, so if they think you can follow the japanese part it rather flusters them.
Actually japanese is much harder than welsh, because (a) the body language and cultural context are very important and quite alien to Europeans and (b) it is a 'tonal' language and the pronounciation is critical, hence Terry Pratchett's recurring 'your wife is a blue hippo' joke. The real effect of this is simply that you are quite unintelligible if your pronounciation is wrong in quite minor respects.
''the stopes soared beyond the range of our caplamps' - David Bick...... How times change .... oh, I don't know, I've still got a lamp like that.