Starting my Early-A Conversion to disc

One big "gotcha" that comes up regularly is a situation of pushrod and whatever master the owner has chosen---does not allow the master piston to fully return. This is VERY important, as the piston MUST uncover the ports drilled in the bottom of the reservoir. The line pressure will not release, otherwise, and the brakes will drag, run hot, or lock up

Make CERTAIN that you take steps to make this so. Mechanical measurements etc.

A popular way is to (carefully as the port(s) can spurt and geysher) take a helper to apply the brakes and release a few times and look for the obvious backflow back up into the master as you look down into it