OK, this is just MY theory, but for years I have thought about this.
First, running hard puts more pressure behind the rings and forces them harder against the cylinder wall. Also, with harder use, different forces occur at different times. In other words, really hittin' it causes the max force on the rods, pistons, cam, etc to happen at slightly different places times, and angles than babying it. This puts wear at slightly different locations on cyl. walls, the cam, the crank etc.
Think of "break in" rather as "final machining" of the parts and it makes sense to create wear patterns and wear locations where they will be run and stressed the most.
Once this admittedly slight "wear in" occurs, all the parts are precisely fit together as they will be run later.
Also, break in is hardly as important today as it was with the much more crude and less accurate machining practices of 30 years ago.
Sounds logical to me - whaddya think ?
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Gotta have a Chevy !In Durham N.C.
Why is there never enough time or money to do it right the first time, but ALWAYS enough to do it over?
Make it look the way you like it, forget what the other guys say!