imagine a shallow "bowl" cut into the chamber. it slows the flame front . NA type cylinder heads speed up combustion to make more power. Nitrous speeds up the combustion also, thats why you reduce the combustion speed by retard timing, reduce quench, etc. Its a balance of too much vs too little.
Most mopar cyl heads have relatively small chambers and a lot of quench areas, (B1, 440-1) they are more geared toward NA