Rotor phasing refers to the alignment of the rotor top and the distributor cap terminal when spark occurs, according to MSD Ignition.
It’s critical to maximizing engine performance. Incorrect alignment can lead to misfire and power loss.
The folks at MSD Ignition have put together a nice visual guide that will show you how to check rotor phasing and how to make adjustments.
You should also watch the MSD video below which does a nice job explaining how to perform rotor phasing.
Check it out!