Camshaft Timing - Timing Chain
| Item | Description |
|---|---|
| 1 | Variable Camshaft Timing (VCT) actuator - Intake |
| 2 | Secondary timing chain guide - Upper |
| 3 | VCT actuator - Exhaust |
| 4 | Secondary timing chain |
| 5 | Secondary timing chain tensioner |
| 6 | Secondary timing chain tensioner guide |
| 7 | Primary timing chain tensioner |
| 8 | Primary timing chain tensioner guide |
| 9 | Crankshaft |
| 10 | Primary timing chain guide |
| 11 | Primary timing chain |
| 12 | Idler sprocket |
| 13 | Secondary timing chain guide - Lower |
There are 2 bushed timing chains used to drive the camshafts via an intermediate idler sprocket. The primary camshaft chain is driven by a sprocket on the crankshaft, which in turn drives the intermediate idler sprocket. The secondary camshaft chain is driven by the intermediate idler sprocket and then passed over the sprockets on the intake and exhaust camshafts. The camshaft sprockets are integrated with the Variable Camshaft Timing (VCT) actuator assemblies.
The primary timing chain has a fixed timing chain guide, which is secured to the cylinder block. A chain tensioner is attached to the primary timing chain tensioner guide. The timing chain tensioner guide can rotate around a pivot bolt. The primary timing chain has a mechanical tensioner operated by spring tension to apply a controlled tension to the timing chain. The primary timing chain tensioner receives pressurized engine oil from the variable flow oil pump with integral vacuum pump.
The secondary timing chain has 2 fixed timing chain guides, which are secured to the cylinder head and the camshaft carrier. The secondary timing chain has a hydraulic secondary chain tensioner, which receives pressurized engine oil from the variable flow oil pump with integral vacuum pump.
The tensioners maintain the timing chains at the correct tension and dampen backlash in the chain tension due to engine deceleration. The timing chains and tensioners are maintenance-free components.
A procedure and special tools are required to make sure that the correct crankshaft to camshaft timing is achieved. Both the primary and secondary timing chains have gold colored links, which are aligned with timing marks on the sprockets.