It is not very likely that all two part studs on my two Argentinan engines were modified for the 60 deg. threads, they all look very standard. It is hard to imagine how they fu***d up these studs, there are other places more likely to ruin , so my guess , still standard. I got me a tap but just for cleaning up all threads in the case after I extracted the brass adapters for the inner studs. This new tap is marked UN 9/16 - 20 , not UNF or other sort and I don´t remember where I got that, from Aliexpress maybe, not Tracy´s . It has same 60 deg profile and I don´t remember if it removed much of alu when cleaning out the threads, unlikely.
Yes, some more metrics now, the 10 mm stainless single studs, 1.5 pitch at bottom, 1mm pitch for top nuts. So now all hollow dowels from bottom to top head bracket with 10 mm studs only. But the 9/16-20 remains in the engine case for taking the 7075 alu adapters. Possibly there are some brass inserts I removed in the remains of parts boxes but would that be a proof to some here ?
Vic
Just looked up Ali, the taps are bicycle crank threads 9/16-20 , see link:
9/16-20 tap
