Best timing is frequently found about 2-3 degrees retarded from where you see detonation.
One low tech way to get relative power indications is what I call my "hill dyno"
I found a steep hill that has a good straight road with a good legal speed limit. I have one that max speed is 55 mph and another where it is 65 mph.
Then I found a stretch were I could pick out some reference points. In my case a couple road signs. I pass the first road sign at a given rpm in a specific gear, and then accelerate at WOT until I reach the second sign. By setting it up so the rpm range and gear put good load on the engine and force it to pull through the rpms you use most on the road, you get a good reasonably safe, and even legal if you set it up right road dyno. Price is right too.
As you gain power your elapsed time and max rpm at the second reference point will both change, time dropping and max rpm going up. Its reasonably repeatable, and sensitive enough to help you find that point where additional ignition advance does not make any significant improvement.
A few days ago I got to watch a friend do a dyno tune and by optimizing ignition timing, and AFR he made more power on 2 less psi boost without detonation. Boost does not always equal more power.
Larry