blueprinting a block is measureing the outside diameter of the main journals to make sure they have a ture roundenss,and the bearing bores,checking the thrust on a crank,the big end of the rod is honed for the same reason the main bearing are to get the right amount of bearing crush in order to facilitate heat transfer,--- well look here im looking for clearence in my motor like piston to head clearence i want .032 to .040, piston to wall clearence i want .004 of a inch and so on. and yes i know the pulley, crank and flywheel gets balance all at one time because oil on the crank make it off balance so its a good idea to get it as close as you can. friction robs you of hp.