Abstract: A combustion liner suitable for an automotive gas turbine has variable primary and secondary air admission ports through the wall of the liner. The areas of these sets of ports are varied jointly by two annular valve sleeve assemblies reciprocable on the surface of the liner. Each valve sleeve assembly comprises an outer rigid ring, four approximately quarter-cylindrical valve plates extending around the outer surface of the liner within the ring and coupled to the ring for reciprocation by it, and a leaf spring disposed between the ring and each valve plate to hold the valve plate in contact with the liner.