Abstract: An internal combustion engine having: a cylinder block defining a cylinder; a cylinder head defining a seat; a piston; a crankshaft, the piston, cylinder, and cylinder head defining a variable volume combustion chamber therebetween; an air intake passage; an exhaust passage; a fuel injector; and a combustion pre-chamber housing connected to the cylinder head and extending in part into the combustion chamber. The housing has: a tapering portion; and a tip connected to the tapering portion. The tapering portion abuts the seat. The tapering portion tapers toward the tip. The seat and the tapering portion of the housing have corresponding shapes. The housing defines: a combustion pre-chamber; and at least one orifice fluidly communicating the combustion pre-chamber with the combustion chamber. A spring biases the tapering portion of the housing against the seat of the cylinder head. A spark plug is connected to the combustion pre-chamber housing.