Abstract: A pre-combustion chamber assembly for an internal combustion engine is disclosed having an inner housing having a receiver for receiving a spark plug and an inlet for fuel. A connector is provided for securing the pre-combustion chamber in a spark plug well of the internal combustion engine. An outer housing has a first end and a second end and extends around the inner housing, with a chamber being defined between the inner and outer housings. The outer housing is releasably retained around the inner housing so as to allow relative movement between portions of the inner and outer housings while maintaining the integrity of the chamber. A method of modifying an internal combustion engine and an internal combustion engine incorporating the pre-combustion chamber are also provided.