We present a design and parameter study on 3D-printed, lost-wax-casted and combustion-powered soft silicone pumps, which are internally cooled by the conveyed liquid. Important factors influencing the pumping performance such as gas mixtures, feed rates, and actuation frequencies were thoroughly studied. Furthermore, we reinforced some of the here presented pumps with aramid fabrics in order to achieve partial blocking of the elastomeric flexibility upon combustion expansion. This design measure dramatically increased the pumping capabilities and allowed continuous conveying of water to 13 m (corresponding to 42 ft) of height. We were able to stably operate these novel pumps for more than 30 000 combustion cycles. Therefore, they represent a further step toward long-term stable soft machines with dense power characteristics.