Tools Required

• J 39946  Crankshaft Rotation Socket
• J 44214  Flywheel Holder

Setting the camshaft timing is necessary whenever the camshaft drive system has been disturbed such that the relationship between any chain and sprocket has been lost. Even when only one sprocket is involved the following procedure should be observed since one crankshaft rotation will not provide conditions where correct timing can be confirmed.

The camshafts and crankshaft events are correctly timed when the relationships shown exist. The following procedure explains how to establish this condition. Correct timing exists when the crank sprocket and the intermediate shaft sprocket have their timing marks aligned and all four camshaft drive pins are perpendicular (90 degrees) to the cylinder head surface.

1. Remove the following components for access:
   • The left camshaft cover. Refer to Camshaft Cover Replacement - Left .
   • The right camshaft cover. Refer to Camshaft Cover Replacement - Right .
   • The engine front cover. Refer to Engine Front Cover Replacement .
   • The three chain tensioners. Refer to Primary Camshaft Drive Chain Tensioner Replacement , Secondary Camshaft Drive Chain Tensioner Replacement - Left  , Secondary Camshaft Drive Chain Tensioner Replacement - Right  (the tensioners may be in their installed positions but must be fully retracted).
   • The oil pump. Refer to Oil Pump Replacement .
   Fig 1: Installing Primary Camshaft Drive Chain & Sprockets

   Courtesy of GENERAL MOTORS CORP.
2. The primary and secondary chain guides should be reinstalled if previously removed.
3. Rotate the crankshaft (2) until the sprocket drive key (1) is at approximately the 1 o'clock position. Use the J 39946  to rotate the crankshaft (2).
4. Install the crankshaft and the intermediate shaft sprockets to the primary drive chain with their timing marks adjacent to each other.
5. Install the crank and intermediate sprocket assembly (4) over their respective shafts.
6. Rotate the crankshaft (2) as necessary to engage the crankshaft key (1) in the sprocket without changing the relationship of the timing marks to each other. Use the J 39946  to rotate the crankshaft (2).
   CAUTION: Refer toFASTENER NOTICE .
7. Install the camshaft intermediate sprocket bolt (3).

   Tighten 

   Tighten the camshaft intermediate sprocket bolt to 60 N.m (44 ft lbs).

8. Install the primary camshaft drive chain tensioner or release the tensioner shoe.

   Tighten 

   Tighten the primary camshaft drive chain tensioner bolts to 25 N.m (18 ft lbs).

9. Ensure the timing marks (1) are aligned vertically.
10. Install the J 44214  to lock the crankshaft in this position. If the engine is on a stand, an alternate method should be devised.
    Fig 2: Identifying Primary Timing Marks

    Courtesy of GENERAL MOTORS CORP.
11. Route the secondary drive chain for the LH cylinder head over the inner row of intermediate shaft teeth.
    Fig 3: Routing Secondary Drive Chain For LH Cylinder Head

    Courtesy of GENERAL MOTORS CORP.

    Important:  The RE camshaft sprocket must contain the camshaft position sensor pick-up.

12. Route the secondary drive chain over the chain guide and install the exhaust camshaft sprocket to the chain such that the camshaft drive pin engages the sprocket notch marked LE (left head exhaust). There should be no slack in the lower section of the chain and the camshaft drive pin must be perpendicular to the cylinder head face.
13. Install the intake camshaft sprocket into the chain so that the sprocket notch marked LI (left head intake) engages the camshaft drive pin while the pin remains perpendicular to the cylinder head face. A hex is cast into the camshafts behind the lobes for cylinder -1 (or -2, LH) so that an open end wrench may be used to provide minor repositioning of the camshafts.
14. Loosely install the exhaust camshaft sprocket retainer bolt.
15. Loosely install the intake camshaft sprocket retainer bolt.
    Fig 4: Identifying Sprocket Drive Pins At Top Rotation

    Courtesy of GENERAL MOTORS CORP.
16. Install the secondary camshaft drive chain tensioner or release the tension on the shoe.

    Tighten 

    • Tighten the secondary camshaft drive chain tensioner bolts to 25 N.m (18 ft lbs).
    • Tighten the camshaft sprocket bolts to 120 N.m (89 ft lbs).
    Fig 5: Installing Secondary Camshaft Drive Chain Tensioner

    Courtesy of GENERAL MOTORS CORP.

    Important:  The RE camshaft sprocket must contain the camshaft position sensor pick-up.

17. Route the secondary drive chain for the right side cylinder head over the outer row of the intermediate shaft teeth and repeat steps 11 through 15 for right side camshafts. Right side camshaft sprockets are identified as RI (right intake) and RE (right exhaust). In addition the RE sprocket must contain the camshaft position sensor pickup.
    Fig 6: Routing Secondary Drive Chain For Right Side Cylinder Head

    Courtesy of GENERAL MOTORS CORP.
18. Ensure all timing marks are properly aligned.
19. Install the following components:
    • The oil pump. Refer to Oil Pump Replacement .
    • The engine front cover. Refer to Engine Front Cover Replacement .
    • The right camshaft cover. Refer to Camshaft Cover Replacement - Right .
    • The left camshaft cover. Refer to Camshaft Cover Replacement - Left .
    Fig 7: Identifying Drive Chains Routing

    Courtesy of GENERAL MOTORS CORP.