Here is a test on the box going in my car. It’s wired up exactly as it will be in the car. I forgot I recorded this, as I had forgotten if I even tested this box and was going to pull the box back off the car just to test it.
This just happens to be a very good box.
If you watch it I have the nasty habit of using distributor and crank degrees interchangeably and that’s bad.
Every tic mark is 1 distributor degree or two crank degrees regardless of how I screw it up.
But the box does retard. If someone really wants to throw up in their mouth I can do a test with the orange box hanging on the wall and you can see what massive, early retard looks like. I think that box retards at least 8 degrees by 7k or something. It’s pretty nasty.
I watched your video again. I can’t hear exactly what you are saying in the video but in the post you describe this as a test for box retard. I don't see how this is measuring box retard as it seems the way you are testing it the box is operating independent of the distributor machine. The timing retard you are seeing is coming from the combination of your distributor and the distributor machine itself. You would need to measure from the secondary side of the coil to include the module or box.