engine break-in contradiction

Originally Posted by ZKdoggZ

Manufactures are making engines with much higher tolerances today. Where cylinder clearances used to be in the thousands of an inch, now its in the ten thousands. Bores are rounder and straighter. There is know reason to baby a newer engine, it will actually hurt. You need cylinder pressure to drive the rings out onto the bore, which actually shaves the bore into a perfect fit. By babying it the rings will only rub and burnish the surface leaving a less then Ideal finish. So ... keep the revs below 4000 the first 300 miles, then drive it ... accelerate with meaning for the next 2500 miles and your all set. This is how all High Performance engines are broken in, and all engines today can be considered a high performance engine since they pull more power out then there predecessors ever did.