I learned about this as a kid from my dad when an ice storm took out our power for a couple days. He cooked dinner on the block of his truck that night. I've done burgers and bratwurst on road trips a handful of times. I never had great luck straight on top of the engine block like they do in the video, dunno if there's more breeze at the top or what. If you can find an exhaust manifold that's a bit lower, you get much better heat. Probably obvious, but make sure you don't obstruct any moving parts, or position something that could fall into a moving part. The texture of any meat is going to end up a little weird, you're not going to get a sear or anything and it's going to be cooked unevenly, but with some salt and pepper it's totally fine. That said, doing this with chicken like they suggest in the video seems insane to me, due to the inconsistent heat and cook time. I wouldn't do this with anything that I wouldn't be okay with eating slightly undercooked if need be.