An essential part to keep the timing chain in tension and stopping  it from clattering about burring over the oiler pipe thus stopping oil from lubricating the chain and making the stuation much worse and the chain will hit the timing cover creating alloy swarf further damaging the engine that assuming the chain does not break and seize the engine!!Dont forget to replace the spring also see 101/1. Note Now available as a complete kit see Part No 100/1/1