Every four-stroke engine needs a way to keep the camshaft(s) synchronized with the crankshaft. Most engines use either a timing belt or a timing chain. Knowing which one your engine uses, and how each one wears, helps you plan the right repair.
Timing Belts
A timing belt is a reinforced rubber belt with teeth that runs outside the engine behind a cover. Belts are quiet and lightweight, but the rubber ages with time and mileage. For that reason, vehicle manufacturers specify a replacement interval for timing belts. On many engines, the timing belt also drives the water pump.
Timing Chains
A timing chain is a metal chain that runs inside the engine and is lubricated by engine oil. Chains are designed for long service life, but they can still wear and stretch, especially when oil changes are neglected. Tensioners and guides also wear over time.
Warning Signs
- Rattling noise from the front of the engine, often most noticeable at startup (chain systems)
- Check engine light with camshaft/crankshaft correlation codes
- Rough running, misfires, or difficulty starting
- Visible cracking, fraying, or missing teeth on a belt during inspection
Interference Engines
In an interference engine, the valves and pistons share space in the cylinder at different times. If the timing belt or chain fails, the pistons can strike the valves and cause major engine damage. Following the manufacturer’s maintenance schedule is especially important on these engines.
What to Replace Together
Because the labor to reach the timing system is significant, the related wear parts are commonly replaced at the same time. Belt systems typically include the belt, tensioner, and idler pulleys, and often the water pump. Chain systems typically include the chain(s), sprockets, tensioners, and guides, along with the related seals and gaskets.
Evergreen Timing Kits
Evergreen offers timing chain kits and timing components configured by engine. Kit contents vary by part number. Use the Evergreen eCatalog to confirm which system your engine uses and to find the right kit.
