It's not every day you get to hand-build a 638 HP LS9 engine that'll slip under the hood of a Corvette ZR1. Yesterday was one of those days. Here's how the magic is made.

Yesterday we drove over to GM's Performance Build Center (PBC) in Wixom, Michigan to build an LS9 engine — the most powerful production engine GM's ever built — and the 638 HP beating heart powerplant underneath the hood of the Corvette ZR1 — all while being taught the tricks of engine assembly trade by the man who's built more LS9's than anyone else.

Here's how the magic's made.