Timing belt kits contain everything needed to replace the timing belt and its associated parts. It connects the crankshaft to the camshaft(s), which in turn controls the opening and closing of the engine's valves. The kit generally includes the belt itself, idler and tensioner pulleys which are necessary to maintain or decrease slack as needed, and bolts needed to secure everything in place.
When a timing belt is replaced, correct belt tension is critical. If the belt is too loose, it will whip, too tight and it will whine and put excess strain on the bearings of the cogs. In either case belt life will be drastically shortened. For this reason it is important to replace all the timing components, rather than just the timing belt
A timing belt kit is needed if the car manufacturer specifies that all parts connected to the belt should also be changed. Failure to change the timing belt when necessary can result in major engine damage. Show Less