Abstract: A heat exchanger core assembly suitable for use in a motor vehicle and the like cooling system. The assembly has a multiplicity of parallel heat transfer fins pierced by a large number of liquid-filled tubes to be cooled. The leading edges of the fins are overturned to provide venturi-shaped inlets for the cooling air effective to increase the air flow velocity over the fins. These overturned edges have an outer broad surface lying in a plane normal to the air passages which surface is readily cleared of insects unable to enter the venturi throat.