RE: ringed engine break in?
Dave:
What Bruce is neglecting to mention, or even consider, is that a one thousandth inch error on a four inch small block Chevy bore is equivalent to a 0.000001" error on the 0.401" bore of a Cox 0.049 engine. Roy Cox claimed one millionth inch accuracy, but I've measured as much as a tenth of a thousandth difference in brand new Cox pistons. Cox' claim was mainly hype, but they were close enough that most could be run without hand fittung.
And yes, I was on speaking terms with Roy Cox in the early 1960s, Bruce. Also Johnny Brodbeck, Bill Wisniewski, and... Want to drop some more names, Bruce?
Bill.