In a HEMI head, the spark plug is normally located at the top of the combustion chamber, and the valves open on opposite sides of the combustion chamber. Most cars prior to the 1950s used what was known as a flat head, and many lawn mower engines still use the flathead design today ...
Many states require that motorcycle riders wear helmets. Helmets perform two functions in a crash. The outer shell, which is constructed of fiberglass or injection-molded plastic, distributes energy from an impact across a wider area. An inner lining made of polystyrene absorbs most of the shock...