Top End Noise
1.) Loud, rhythmic clatter
2.) Slapping or thumping coming from the front of the engine
3.) Hum that whirs and whines, rising and falling in pitch with the RPM
4.) Loud, cycling, valve rattle
5.) One clear clack when a certain valve opens
6.) Irregular clacking or knocking noise
Bottom End Noise
7.) Irregular knock at idle that sounds louder or softer when moving the clutch pedal
8.) Rapid, dull pounding that is steady and increases with load
9.) Sharp knocking that is easier to hear at idle; the knock will be audible at top dead center and the bottom dead center if you ground the spark plug of the affected cylinder
10.) Sharp clattering knock; the sound can be continuous at idle or only happen when the throttle suddenly closes
11.) Hollow metallic clatter; it will be louder when the engine is cold