Well, you could start by making them a bit longer, maybe. If you want more physical detail, I'd add an extrusion to the top-inner parts, and make it another part of the engine, and let it sort of "hang" over the back...
Hard to describe...Ill try this.
current engine (viewed from back)
************
************
New engine (from back)
******
************
************
(from side)
***********
**********
**********
Hope that helps a bit! Maybe add some ridges, or out-of-plane features, like an extrusion slanting out of the bottom. Hard to describe 3D ideas in text.
