Interesting; my Street Hemi had a measured 10.8:1 CR, 36 degrees with vac advance, and never pinged or detonated on even Calif 91 octane,
It did have a pretty big cam (IIRC, around 260 @ .050 & .547 lift), though, which no doubt bled off some dynamic CR.
One of the crispest-sounding engines I've ever owned, after a little stagger jetting.