A diesel engine includes a cylinder block having a cylinder cavity defined therein. A cylinder head is coupled to the cylinder block and includes a lower semi-hemispherical surface defined thereon that defines an upper boundary of a combustion chamber. The engine includes a piston slideably disposed within the cylinder cavity that includes a piston crown having an upper surface configured to define a first portion of a lower boundary of the combustion chamber. The upper surface of the piston crown includes an axi-symmetric semi-hemispherical shape configured to correspond to the lower semi-hemispherical surface of the cylinder head.