Never Start A Rebuilt Engine Without Doing This

Why do mechanics spin freshly rebuilt engines with power tools?! 🏎️🔧
When mechanics finish assembling a combustion engine, starting it completely dry is a massive mistake. If the internal bearings are too tight, or if the metal piston rings lack lubrication, the sheer friction of a dry start will instantly score the cylinder walls and destroy the block!
To safely verify their work, mechanics will rotate the heavy steel crankshaft manually to prime the system. While most use a standard hand wrench, using an electric impact drill rapidly spins the rotating assembly! This brilliant delivery method forces the oil pump to send vital lubrication to the top of the engine, lets the builder visually confirm there is zero internal binding, and proves the mechanical timing is perfectly set before fuel and spark are ever introduced!