Modern Combustion chambers already promote swirl in the air flow with the focal point right around the spark plug. Cutting grooves in the combustion chamber face just lowers your compression, increases heat loss from the combustion gasses, and weakens your head.
Even on an older engine, this technique has been shown to do nothing to improve peak power or efficiency. I don't have the link, but someone sacrificed an engine and tested this on an engine dyno. It will move the rpm of your peak power and torque slightly however.
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