Simply use marine "Shrink Wrap", after placing a few bags of a good de- humidity crystals inside, costs about $50 per engine, I have picked up a DC9 after three years in a very gritty/dusty place and had no crap whatsoever inside the wrap. Use heavy duty wrap and if its going to be in long term storage use two layers, its a good idea to write a note on the wrap to remove desicant bags before starting the engine, dont ask how I know this!