Here's a couple pics of my old one, had to dig it out.....
I used a pnuematic air muffler for the end cap on the motor tube, that way when the engine kicked it's blast it just pops the motor out of the back of the car.... Wings were added for the fun of it as I was a kid then.... Needless to say the hood and grille were blown off as it went airborn a couple times and landed nose first!!!