【正文】 組成，包含Inter 慣性，慣量Radius 半徑，范圍Circular 圓形的Steel band 鋼圈Fit into 放入，放進Groove 凹槽Piston pin 活塞銷Pin boss 活塞銷凸臺Withstand 抵抗Hollow 空的Brunt 沖力Crown 活塞頂Skirt 裙部Ring land 環(huán)帶Concave 凹的，凹入的Dome 圓頂Recessed 隱蔽的Cylinder wall 氣缸壁Cylinder bore 缸筒Splash 飛濺chromeface 表面鍍銀的Untwist 朝相反方向的In place 在適當(dāng)位置Chromeplated 鍍鉻的Forge 偽造，仿造Crankpin 曲軸銷Bush 軸瓦，套筒Bronze 青銅Crankshaft journal 曲軸軸頸Steelbacked 鋼背的Lead 鉛Tin 錫Splint 切口，中斷，分配，分離In conjunction with 連同Reciprocating motion 往復(fù)運動Rotary 旋轉(zhuǎn)的Carbon steel 碳鋼Journal 軸頸Align with 匹配Overlap 重疊Timing gear 正時齒輪Throw 擺幅Vice verse 反之亦然Impulse 脈沖Space out 隔開，分隔Through out 遍及Diagram 圖表Firing order 點火順序Companion 成對Circumference 圓周 Valve System The valve system is made up of those parts needed to open and close the valves at just the right time . Valve Operation To coordinate the fourstroke cycle , a group parts called the valve train opens and closes the valves ( moves them down and up , respectively ) . These valve movements must take place at exactly the right moments . The opening of each valve is controlled by a camshaft .1. Camshaft(OHC) Valve Train OverheadThe cam is an eggshaped piece of metal on a shaft that rotates in coordination with the crankshaft . The metal shaft , called the camshaft , typically has individual cams for each valve in the engine . As the camshaft rotates , the lobe , or high spot of the cam , pushes against parts connected to the stem of the valve . This action forces the valve to move downward . This action could open an inlet valve , or open an exhaust valve for an exhaust stroke . As the camshaft continues to rotate , the high spot moves away from the valve mechanism . As this occurs , valve spring pull the valve tightly closed against its opening , called the valve seat .Valve in modern car engines are located in the cylinder head at the top the engine . This is known as an overhead valve (OHC) configuration . In addition , when the camshaft is located over the cylinder head , the arrangement is known as overhead camshaft (OHC) design . Some highperformance engine have two separate camshafts , one for each set of inlet and exhaust valves . These engines are known as overheadcamshaft (DHOC) engine .2. Pushrod Valve Train The camshaft also can be located in the lower part of the engine , within the engine block . To transfer the motion of the cam upward to the valve , additional parts are needs . In this arrangement , the cam lobs push against round metal cylinders called follower upward ( away from the camshaft ) . The cam follower rides against a push rod , which pushes against a rocker arm . The rocker arm pivots on a shaft through its center . As one side of the rocker arm moves up , the other side moves down , just like a seesaw . The downwardmoving side of the rocker arm pushes on the valve stem to open the valve . Because a pushrod valve train has additional parts , it is more difficult to run at high speeds . Pushrod engines typically run at slower speeds and , consequently , produce less horsepower than overheadcamshaft designs of equal size . ( Remember , power is the rate at which work is done .) Valve Clearance When the engine runs in pression stroke and power stroke , the valves must close tightly on their seats to produce a gastight seal and thus prevent the gases escaping from the bustion chamber . If the valves do not close fully the engine will not develop fill power . Also the valve heads will be liable to be brunt by the passing hot gases , and there is the likelihood of crown touching an open valve , which can seriously damage the engine . So that the valves can close fully some clearance is needed in the operating mechanism . This means that the operating mechanism must be able to move sufficiently far enough away from the valve t allow the valves to be fully closed against its seat by the valve spring . However , if the clearance is set too great this will cause a light metallic taping noise . Valve Timing The time at which valves open and close ( valve timing ) and the duration of the valve opening in stated in degrees of crankshaft rotation . For example , the intake valve normally begins to open just before the piston has reached the top dead center . The valve remains open as the piston travels down to BDC and even past BDC . This is intake valve duration .An example of this could be stated as follows : IO at 17BTDC , IC at 51ABDC ( or , intake opens 17before top dead center , intake closes 51after bottom dead center ) . Intake valve duration in this case is 248 of crankshaft rotation .This leaves 129 duration for the pression stroke since pression ends when the piston reaches TDC . At this point the power stroke begins . The power stroke ends when the exhaust valve begins to open approximately at 51 before bottom dead center . The duration of the power stroke in this case is also 129 . Since the exhaust valve is opening at 51 BBDC , this begins the exhaust stroke . The exhaust stroke continues as the piston passes BDC and moves upward to past TDC . With the exhaust valve closing at 17 TTDC , the duration of the exhaust stroke is 248 . It is apparent from this description that the exhaust valve stays open for a short period of time during which the intake valve is also open . In other words , the end of the exhaust stroke and the beginning of the intake stroke overlap for a short period of time . This is called valve overlap . Valve timing and valve overlap vary on different engines. Opening the intake valve before TDC and closing it after BDC increase the fill of airfuel mixture in the cylinder . Opening the intake valve early helps overe the static inertia of the airfuel mixture at the beginning of the intake stroke , while leaving the intake valve open after BDC takes advantage of the kentia of the moving airfuel mixture . This increa