There was some discussion a couple of weeks ago about shimming the Plasma III electronic ignition sensor backing plate that mounts on the engine baffling behind the propeller.  While I had the cowling off on my Legacy with an IO-550 EXP engine yesterday, I took this photograph:

 

 

The bottom of the sensor plate mounts to a double layer of aluminum baffling.  The photo shows that I cut a shim the same thickness as the baffling and mounted it under the upper part of the backing plate, where it mounts to only a single layer of baffling.  This allows the backing plate to be parallel with the plane of the rotation of the propeller.

 

Dennis Johnson

Legacy, 150 hours