Balancing and Blueprinting. That term has come to be used over the years for a high performance engine. Meaning it is 'better' than a stock engine.

What it means to a machinist and engine builder is that the reciprocating parts have been balanced. Yes, you balance a single cylinder engine. That is what the counterweight on the crankshaft is for. A multi cylinder engine has all the rods and pistons weighing the same and crank weights properly counterbalancing the weight of the reciprocating mass.

"Blueprinting" the engine means all technical specifications of the engine design have been met. That is not a big deal though. Because engine specs allow a tolerance, a variation of dimensions. Ideally, the dimensions are held to the minimum. But if they are anywhere within the envelope the engine is technically "blueprinted."