Thought you readers might be interested in this cutaway of the first production hemi and the information that the Museum put up about the engine. According to the museum info this is a 1951 Chrysler "Firepower" engine. The Chrysler engineers designed an engine using the hemi combustion chamber for a few basic reasons. 1) Volumetric efficiency in a hemi cylinder head was better because of larger valves located across from each other allowed the engine to breath better and created a cross flow between the intake and exhaust ports 2) The compact design of the hemi chamber and location of the spark plug allowed more complete burning of the fuel air mixture and 3) A hemispherical combustion chamber minimizes engine heat loss because the smallest surface area that will contain a given volume is a sphere. Less surface area means less heat loss. It was right in 1951 and it still is today.