thank you your engine serial number is *****
you may want to use ther stc injector flush kit from cummins to clean injectors prior to replacing them
The correct setting procedure for an stc engine is as follows..
The valves and injectors on the same cylinders are not adjusted at the same index mark on the accessory drive pulley on STC engines.
One pair of valves and one injector are adjusted at each pulley index mark before rotating the accessory drive to the net index mark.
Two crankshaft revolutions are required to adjust all the valves and injectors.
Be sure to loosen the adjusting screw enough so there is no preload on the injector. This will be accomplished when the rocker lever is loose enough to move
Place the STC tappet adjusting tool, Part Number(NNN) NNN-NNNN or equivalent, on the upper surface of the STC injector top-cap. Rotate the tool around the tappet until the tool's locating pin is inserted into one of the four holes in the top of the tappet. see pic below
Apply thumb pressure to the tool handle to hold the tappet in the maximum upward position.
tighten the adjusting screw while holding the tappet in the maximum upward position. tourque to 6 in lbs