See Through Engine - 4K Slow Motion Visible Combustion

Mikka installed an inch-thick transparent glass head onto a 3 hp flathead Briggs and Stratton engine, then set up a Phantom 4K high speed camera to create videos of the combustion process that are 150 times slower than real time. You can see the valves move, the fuel entering the chamber and the spark igniting it. For comparison, he burns gasoline, rubbing alcohol and acetylene.
Unfortunately, the last one burned so violently it wrecked the head before he could try the one he wanted to the most: tequila. But if you want to see what happens if you heat up a bottle of beer with an acetylene torch, he’s got you covered.