NOTE: The ATS 2E Differential Pressure Tester has a .040” orifice and is the appropriate tool for ALL Textron Lycoming engines as indicated in their Service Instruction SI-1191A. Teledyne Continental engines require our model 2EM to comply with their Service Bulletin SB03-3. For all other makes of engines, consult FAA AC43.13 REV 1B for guidance in selecting the proper instrument for your engine.