Gas turbine engine systems and related methods involving heat exchange are provided. In this regard, a representative heat exchange system for a gas turbine engine includes: a heat exchanger; and a flow restrictor operative to selectively restrict a flow of gas flowing along an annular gas flow path; in an open position, the flow restrictor enabling gas to flow along the gas flow path and, in a closed position, the flow restrictor restricting the flow of gas such that at least a portion of the gas is provided to the heat exchanger, the heat exchanger being located radially outboard of the flow restrictor.