Drilled a series of holes to 7/16" dia for 1/4" NPT tap. Stuffed a rag in the filler port and held a vacuum nozzle on bit/tap to prevent chips from falling into engin. Hole located 1-1/2" below fill fitting. Tap was very easy, used a 1/2" socket to drive the end of the tap. Attached NPT to AN-6 flare, 90 degree elbow.
