PSB - You kiddin me! At 13:1 and the revs I was running all I was hearing (and everyone within 3 miles of me) was DETONATION! It sounded like a freakin CUP car - it was bad! No one ever asked me if I had a "427" when I pulled up - it embodied everything a BB 427 could be - LOUD! Seriously, I really didn't hear it but it was loud (and fast)!
At 11:1 it's still nice but not quite what I had grown accustomed too. Good call on changing the heads.
Enjoy!