When will it blow???

While engine designs vary, I have a good ear after 4 years of music to call 5 engines blowing within a 10 lap margin total just by tone alone! Ease of flow, but with minor restriction by load only sounds a bit better than overloaded or stressed to the max freely with too much gear! Neither is good for long with added stress! Cubic inches has tone as well as stroke verses bore! I can't sing or play a lick but I am listening to every engine's tune on the track! Setting timing by ear to tune and tone get us a few more horses! Always back it down 2-4 degrees from where it sounds best at 5,000 as it is not loaded yet! This doesn't  work if running a power valve in your carb! Any raise in timing can produce more vacuum and cause a shut-back in fuel causing a lean condition if not kept loaded! No power valve to blow or go lean when already there protects any engines from middle of the road settings!