Brian,


For a certain time, MVVS had removable studs in these engines, that had to bolt into the 7 and 8 mm front journal...
So the 6 mm thread was about the largest they could use.

It was well made and very hard. It held up pretty well.

Then there was, on the .40-.49, a one-piece crankshaft, with the same 6 mm thread... It occasionally broke while tightening the prop-nut...
So they went to 7 mm after about a week.

This size is strong on a .40-.53!

Nothing to comment about the 8 mm thread size.