A liquid adhesive dispensing system operable for more uniformly applying liquid adhesive foam onto moving substrates, notwithstanding changes in line speed, adhesive liquid flow rates, or foaming/atomizing air pressures. The illustrated liquid adhesive system includes a header having a plurality of air atomizing spray guns; the spray guns each having a respective variable speed positive displacement pump for directing a metered quantity of liquid adhesive from a liquid adhesive supply to the respective spray gun; and a control for controlling the operating speed of the positive displacement pumps in relation to the speed of the moving substrate and the foaming/atomizing air pressure to the spray guns in relation to the operating speed of the positive displacement pumps. The control further is operable for monitoring pressures across the positive displacement pumps for insuring the accurate direction of metered quantities of liquid to the spray guns. The spray guns are adapted for enhanced liquid adhesive foaming and atomization, and the header is convertible into a closed housing structure effective for containing cleaning and purge liquids during an automatically operable cleaning cycle of operation.