英语翻译
Early manufactures of engines,because of lack of koowledge and equipment in casting techniques,were only able to produce an engine assembly having separate cylinder castings,all mounted upon crankcase.While this method is still used for some air-cooled engines,it is not really practical for a liquid-cooled engine.However,as manufacturing techniques have improved,the while construction[cylinder block and crankcase]is produced in one assembly.Cylinder block for modern liquid-cooled engines are cast as single units.求大神们准确的帮我翻译,要准确啊