MOCA Timing Chain VVT Kit for 02-04 Chevrolet Trailblazer 4.2L & 02-04 GMC Envoy XL 4.2L & 03-04 Isuzu Ascender 4.2L & 02-04 Oldsmobile Bravada 4.2L

What does a timing chain do?

• A timing chain synchronizes the rotation of the crankshaft and camshaft(s) ensuring proper timing and allows the engine's valves to open and close during each cylinder's firing. The chain is located inside of the engine and needs to be lubricated by the oil in the engine, making oil maintenance important as well. Every time you use the engine, the timing chain is in use

When does a timing chain need to be replaced?

The timing chain normally needs to be replaced between 80,000 and 120,000 miles unless there is a specific problem. Issues with the chain are common in higher mileage vehicles. If driving an older vehicle, or one with close to 100,000 miles, it is recommended to look for symptoms of the timing chain going bad or failing.

Signs a timing chain needs to be replaced include:

• Later model VVT applications will generate engine codes and check engine lights prior to engine rattle
• Older, pre-VVT applications will generate engine rattle

Should I also replace sprockets and tensioners?

• Yes, MOCA recommends that all components of the timing system be replaced at the same time. Using a worn sprocket may result in the chain not meshing with the worn sprocket, which could result in poor engine performance. MOCA offers a wide range of complete timing chain kits for majority of vehicles on the road today

Are these chains coming with timing marks?

• Each chain has a Timing Chain mark for easier installation. When changing the timing chain or adjusting timing on a vehicle, understanding the timing marks on the crankshaft and camshaft pulleys is key to getting it right