What is a 'blueprinted' engine?

A 'blueprinted' engine is an engine that has been remanufactured to conform exactly to the manufacturer's official specifications - the blueprints, as it were.

You might assume that an engine costing thousands of dollars would already conform to spec. Well, it invariably does, but only within a certain tolerance. Automotive manufactuers already make engine parts (and other components) to tolerances that would have been economically impossible just a few years ago, but economics still plays a factor. To make a 'perfect' engine would require such exacting checks, and such frequent remanufacturing of parts, as to be impossible on a mass scale.

On an individual scale, though, it is certainly possible - given enough time and labor - to build a 'perfect' (really, a near-perfect) engine. Such an engine would realize its peak power output, best fuel economy, and best possible emissions quality due to the 'ideal' interaction between all of the components. Of course, few people need such a machine, and blueprinting is normally reserved for high-performance racing engines.