Having now spoken to someone who actually knows about these things (always a good idea if you don't know what you're doing
) I have a correction to make.
I was correct in saying a fix for worn white-metalled rods was to machine them to take shells, but appear to have simplified things a little by saying the crank could just be swapped for a later one. This would also necessitate the use of the engine cases, which differ from the earlier ones to take larger diameter main bearings. So when I rang my mate, his first question was 'is it a small bearing engine or large bearing engine?'. The way to identify them, without taking them apart, is that the large bearing (therefore the one with replaceable shells) case has a bulbous bit under the timing cover, which is in fact the beefier housing for the beefier bearing.
Kevin agreed with me that my engine should be a '53 according to it's number, but the bottom end denotes it as later than that. 'Take no notice of the numbers' he says, just make sure when you're ordering parts you speak to someone who knows their stuff.'
I went on to put several queries to him, which I'm recording here because a) some of you may find it vaguely interesting and b) I'm bound to forget.
Cams - currently 3325. They've got barely any signs of wear on them, but according to Kevin will make the engine a 'bit flat'. '3134s are the Holy Grail' he said. 'At the very least, use a 3134 on the inlet'.
Cam followers - 'R' ones are preferable. 'R' denotes 'race', and will be stamped on the side of the follower.
Pistons - beware! Hepolite pistons are now produced in China. The rings are made of chocolate. If you're offered 'genuine Hepolite' pistons, walk away. Kevin is also aware of spurious rings coming from Italy, and says that some manufacturers are machining their pistons with shallower ring grooves so that only their rings can be used. Kevin is now re-machining pistons provided by customers, so that proper and trusted ringsets can be used with them. In any event, he says, I should forget the idea of replacing one piston as the ones I have are low compression, much better to have high compression ones.
So it would seem, if I want best performance, I have probably just tripled my estimate of parts needed, just to get the bottom end back together. Of course, I could just continue with the original plan but then Kevin's description of a 'flat, low compression engine' will haunt me for eternity and I will be forever regretting not doing it 'properly' in the first place. Next job is to sit down and price up the parts properly - reality check imminent!
BTW, Kevin is married to the wife's cousin and has run a Triumph restoration business for many years. He was very helpful when I restored my Norton. He doesn't provide services cheaply, not even for family, but his advice is free - he can't help himself, he lives and breathes Triumph. I will still be doing everything myself on this bike, but it's great to have such a knowledgeable bloke to fall back on should I have any questions. Here's a link to Kevin's website -
http://www.heritageclassicmotorcycles.co.uk/ 
