Abstract: A cylinder head has a head portion for attachment to an engine cylinder of an internal combustion engine, and a combustion chamber dome is adjustably received in a central aperture of the head portion. External circumscribed threads on the combustion chamber dome engage corresponding threads in the central aperture of the head portion so that the combustion chamber dome may be adjustably moved into a preselected adjusted position within the central aperture by rotation of the combustion chamber dome with respect to the head portion.A method of adjustably establishing a combustion chamber in a cylinder of 1 an internal combustion engine is also disclosed.