This is a remix of http://www.thingiverse.com/thing:15018. A friend of mine had posted a picture of two rings on facebook, and those rings had engines on them. He tagged his wife and asked if she'd marry him again. I knew that he wasn't going to waste his money on those rings, so I decided to print him a pair of rings.
I printed them with the ring flat, the engine with the front facing down (support for the air cleaner is built in), and the accessories with the front facing up. Support is needed, obviously. When the printing is done, glue the ring to the bottom of the engine, and the accessories to the front. I used an acetone vapor bath to get a nice, glossy finish.