I cooked my first "blockburger" about 45 years ago shortly after reading the PM article cited by Kiowa1.

During the late 60s, I was motoring through western North Carolina with my younger brother when we encountered a traffic stoppage becouse of an accident ahead. Since our foil-wrapped blockburgers had been "grilling" on the engine for over an hour, I popped the hood to see if they were ready to eat. Seeing me with my head under the hood, a state cop at the accident scene wandered over and asked if we were having mechanical problems. "No," I replied, "we’re just taking our lunch off the grill!" The state cop slapped his forehead and exclaimed,"Why didn’t I ever think of that! I’ve been driving patrols for 20 years and could have enjoyed many hot meals cooked on my engine block!"

A couple of years later, "Manifold Destiny: The one! The only! Guide to Cooking on Your Car Engine!" was published. A quick check reveals that a few used copies of the book are available through the Amazon website.