You may not get the engine to knock at 40 degrees total, but it should make more power at 34 - 36 degrees total.
The more advance you run, the more negative work is done on the piston, expanding gas pushing on the piston as it comes up. More modern combustion chambers are running 28 to 32 degrees total for max power. LA Mopars typically use 34 - 36, big blocks need 38. Mag heads if set up properly use low 30s.

The best way to tell this is to use the quarter mile dyno, the fastest mph is the max power setting.

Back in the day, the hot 340s on the street all ran 3.91s.

R.