Originally Posted by
Desert185
The DC-8 has slots inboard of each engine pylon that open and close with flap movement (closed when flaps up and open when flaps extended.
The slots on the DC8 were an early modification for the DC8-12 model. many of the original DC8-11 were then converted, which would involve re-engineering the wings. Initial operations must have shown there was some issue which they overcame.