Modeling with Fire Help / Containing Fire

So I have this golem I made.

To add the effect it was alive instead of an over-sized, disproportionate suit of armor, I decided to put a fire inside of his head and belly, making it resemble a cast iron furnace, in a way. Much to my disappointment, this happened when I tried to put the emitter in him.

The fire is drawn on top of the mesh, completely taking away the effect I was trying to add.

How can I have the fire look like it is inside, instead of… that? Even having the illusion of fire would be good, as long as it is convincing enough.

Post any suggestions below, please.