RE: Norvel spare parts
The different head gasket thicknesses allow you to adjust compression -which as you (hopefully) will have realised through perusing this forum) is often required to fine tune engines for prop fuel and climatic condition variables. A great pity that Norvel seem to be the only manufacturer currently making this option available. If Cox had done it we would have had a lot less trouble over the years! A combination of thicknesses may be required for a particular fuel and prop, and the different thicknesses can be 'ganged' to produce a fairly wide variation in shimming. The better F1C engines in the past required this, and Rossis and in particular the superlative AD 15, had a range of head shims ranging from 0.0015" up to 0.007". If Norvel did the same thing for their smaller engines we'd be even better off!
'ffkiwi'