adjustment is preserved by tightening jam nut 285 against adjusting nut 284 after jam nut 285 has been tightened the pilot stem is again moved down until its flange 274 is shouldered up after which the clearance between nut 284 and the lower end of intermediate pilot housing 114 is checked after jam nut 285 has been finally tightened the stroke of the pilot valve 200 is adjusted the stroke of the pilot valve is adjusted while it is assembled thusly a wrench is inserted through each of the threaded openings 208 of lower pilot housing 128 and is engaged in each of the set screws 214 these wrenches will prevent the pilot valve member 200 from rotating while thread 213 is carefully unscrewed until the seat surface 196 of the pilot valve member 200 just touches the corresponding seat surface 195 of the seat member 170 and adjusting nut 284 just engages the intermediate pilot housing 114 thread 213 is then further made up 1 4 to 1 3 of a turn only after which this adjustment is preserved by tightening the set screws 214 thread 213 being a 20 pitch thread thus the stroke of the pilot valve stem is adjusted to 0 0125 to 0 0167 inch about 0 3175 to 0 4233 millimeter threaded openings 208 are left open for installation of the device 100 in a well since these openings provide passages for communicating casing pressure into the pilot mechanism the upper pilot stem 212 has its lower end portion reduced in diameter as at 286 and is threadedly connected into the threaded bore 276 at the upper end of the lower pilot stem 211 an external annular.