Joe,
To be honest, I can't see the crank clearly enough in the photos to make a
clear decision for you - and I've not yet seen another Spit crankshaft in
the flesh to compare it to. What I will say is that grinding copious
amounts of the lobes away is normal practice for balancing, in some circles
at least. When I worked for Perkins (industrial diesel engine
manufacturers) I watched the process being done in the factory - the guy
would spin the crank up on a machine which would tell him the state of
balance, then he would take it off and just press one lobe or another up
against a grinding wheel for a few seconds, then return to the testing
machine.
Whether this was done in the Triumph factory I don't know, although I have
some vague feeling that they didn't bother trying to balance the cranks at
all after the bearing surfaces had been machined - but I don't remember
where I heard that, so don't take it too seriously. In any case, it is
quite possible that the crank has been re-balanced during some previous
rebuild.
So I wouldn't take the grinding evidence as any issue that should cause you
to think about replacing the crankshaft.
Richard & Daffy
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