Mechanical N14 Parts Help

The stc is there to address smoke at idle & light load conditions. When the engine is working the stc system has no effect on timing.
The timing values I posted refer to the engine base timing. .154 & .172 represent the amount of injector pushrod travel left at 19 degrees btdc. Adjusting that involves changing gaskets between the cam followers & block. In your case you'd have to remove gaskets to move towards the .172 setting. There likely aren't enough there to remove to get what you want. In that case you'd remove the camshaft & install a different key.

 

What's the code #

 

Disadvantage: STCs have cause many people to become an aholic.

 

I used to go to the pump shop and buy a small stack of 50 RPM shims. Four was usually good. Take the button out and buy the next lower number. Keep up with everything so you can put it back it needed. Write it down!
The high and low RPM springs work somewhat in conjunction. When you change the high side that will likely affect the idle RPM. That requires a special tool to adjust. Use a small-medium size cheap straight edge screw driver. Lock it in a vise and knock the handle off of it. Find a compression fitting for plastic tubing that will screw in the back of the governor hosing. Remove the feral and use a piece of vacuum hose or such in its place. As the nut is tightened on the fitting it must become sung on the screw driver shaft. Then reinstall the handle.
The low idle is adjusted with this tool installed and the engine running.