I spotted that one...I rebuilt one of these quite rare engines for a friend not too long ago (it's now in a Goldie 'lookalike' chassis)...
The engine has some potential and looks the part but would require substantial modification to the basic parts (the bottom end and piston particularly) before any real power could be safely extracted from it...
The piston is a real oddball because of the dimensional limitations of the frame and the fact it was designed to be fitted to an unmodified M20 bottom half...
The new piston for the one I rebuilt was commissioned by the owner as a pretty expensive 'one off'...Personally I could think of better and cheaper solutions to that problem...but what do I know?..
...
The engine also has hairpin valve springs particular to the type so these aren't available either...
The Italian 'Gruppo Velox' concern made various versions of the conversion, one being for the 16H, though I've yet to see one of those...
I once tried to buy a complete 'conversion' bike from an Italian dealer but we couldn't come to terms on the price...That one had a Moto Guzzi type parallelogram tubular swinging arm conversion to the original M20 frame as well...
Originally the conversions all went onto ex WD motorcycles left in Italy by the armed forces...This allowed the Italians to skirt around limitations imposed by the allies that did not permit the manufacture of motorcycles over 250cc in the early post war period...I imagine the cheap source of complete machines was useful as well...
One year at Founders Day there was a converted Triumph 3HW for sale...That retained it's original OHV Triumph engine but had the suspension as described above, tele forks and a 'jelly mould' Italian racing tank!......Ian
email (option): ian@wright52.plus.com