 In very early engine designs the valves were "upside down" in the block, parallel to the cylinders.This was the so-called L-head engine design, because of the shape of the cylinder and combustion chamber, also called 'flathead engine' as the top of the cylinder head was flat.The term preferred outside America (though occasionally used there too) was "sidevalve"; hence, its use in the name of the UK-based Ford Sidevalve Owners' Club.