I'd throw 20 bucks at it. Hell, if hondas had quench space I would've done this a while back. Mehbe this is something I can try on my possible geo metro before I dump the diesel in there, :p

Quench
 

I thought a combustion chamber used the "quench" area to control detonation. I would think grinding a groove to allow the flame front to travel into the quench area would be detrimental to the control of detonation. Or would these channels allow gases caught in the quench area to be forced back into the center of the chamber and create more turbulence (swirl) for a more complete burn?