These older engines had smaller carbs than now,so as w8ye says they had better fuel suction. The one I have on the combat plane didn't have a pressure fitting,so I put one on it. Just makes for more reliable running during violent maneuvers. You would have to plug the hole in the front to get enough pressure to be worthwhile. By the way w8ye, these are schnurle ported engines. Up to date for its age.