What does it mean when someone has a rebuild motor that has been blueprinted ??

 

It means every clearance is checked and adjusted accordingly to a higher degree of precision than trusting factory measurements. Along those lines, a cylinder bore would be honed out for a specific piston, rather than just punching it out to the ".020" over size that the piston claims it is, and item balancing everything that rotates or is connecting to something that rotates inside the engine.

 

the end result is a stronger engine that revs more freely (less parasitic loss which means a slight gain in power) and to a higher possible redline (there are other factors that'll limit this, though)