An improved dome-shaped piston head is disclosed characterized by a plurality of channels, depressions, and recesses which enhance the flow of an air-fuel mixture around the piston head in a combustion chamber and the flow of exhaust gases from the chamber. Specifically, the dome-shaped head portion includes a pair of depressions in its intake and exhaust side portions for increasing swirl of the air-fuel mixture. The intake side portion of the piston head also includes first and second channels which cooperate with the intake depression to direct the incoming air-fuel mixture around the piston dome and upwardly into the combustion chamber with swirling turbulence. The exhaust side portion of the piston head includes a pair of tapered recesses on opposite sides of the exhaust depression for directing exhaust gases toward the exhaust opening.