Aged blocks - once upon a time, in the long distant past, in a galaxy far, far away........manufacturers of 'quality', 'up-market' engines used to stack raw block castings up and leave them for a few months before machining them. The rationale was that the stresses induced during the post-casting cooling phase would settle out and any machining carried out would retain accuracy over time. It was always thought that this gave a better finished product.
