So I settle down to clean up the cases prior to assembly, and put cams and followers in to see whats what re bushes etc.
I notice that the tappet feet do not contact the base of the cam by several MM, that explains the loud clatter I had since cams were refaced, so the only way to solve that was to take a bit off the crankcase guides so the stems can sit lower.
Put it all on the gas ring, blow me if I did not spot two more cracks, one under the timing chest, the other by the tappet guide.
Looks like tomorrow I'll bite the bullet and use that wonder alloy solder I bought at Netley the other year;at least they are only small cracks.
Seems I got sub standard casting on my model 1 :'(