Accepted Answer

Timing Chain Alignment View Full Image

Timing Chain Guides View Full Image

Fig. 16 Timing Chain Tensioner Spring & Retainer View Full Image

Camshaft Sprockets View Full Image

NOTE: GM does not provide timing chain marks, or information to perform timing chain service without the special tools shown in this procedure.

SPECIAL TOOLS REQUIRED (or equivalents):

• J-36008, Camshaft sprocket timing alignment pins.
• J-39579, Camshaft sprocket wrench.

CAUTIONS:

• The timing chain on the engine is not to be replaced with the timing chain from any other model year. The timing sprockets are different on this engine and the shape of the links matches the sprockets. Engine damage may result if the wrong timing chain is used.
• The timing chain and crankshaft sprocket MUST be marked so that they are reinstalled with the same side facing out at the time of reassembly.
• Failure to follow the removal and installation procedures could result in severe engine damage.

REMOVE OR DISCONNECT

1. Negative battery cable.
2. Front cover, refer to Timing Cover / Service and Repair .
3. Rotate crankshaft in clockwise direction until camshaft and crankshaft timing marks are aligned.
4. Timing chain guides.
5. Raise and support vehicle.
6. Ensure slack in timing chain is above tensioner assembly, then remove chain tensioner. The timing chain must be disengaged from grooves in tensioner shoe to permit removal of shoe. Position a suitable screwdriver under timing chain while pulling shoe outward. If difficulty is encountered in removing tensioner shoe, proceed as follows:

• 1. Lower vehicle, then while holding the intake camshaft sprocket with J-39579, remove sprocket bolt and washer.
  2. Remove washer, then install bolt into camshaft by hand.
  3. Position a suitable three jaw puller into intake camshaft sprocket relief holes and remove sprocket.

CAUTION: Do NOT pry on camshaft sprocket as damage to sprocket or timing chain housing may result.

1. Tensioner assembly attaching bolts and tensioner assembly.
2. MARK CRANKSHAFT SPROCKET AND TIMING CHAIN outer surface for reassembly.
3. Timing chain.

INSTALL OR CONNECT

1. Intake camshaft sprocket onto camshaft with surface marked during removal showing.
2. Intake camshaft sprocket retaining bolt and washer, torque to 70 Nm ( 52 ft lbs ) while holding the sprocket with J-39579 (if removed).
3. Timing pins, J-36008, through holes in camshaft sprockets into holes in timing chain housing to position camshafts for proper timing. If camshafts are out of position and must be rotated more that 1/8 turn to insert timing pins:

• 1. Crankshaft MUST be rotated 90°clockwise off of TDC in order to give the valves adequate clearance to open.
  2. Once the camshafts are in position and the timing pins have been installed rotate crankshaft COUNTERCLOCKWISE to TDC.

CAUTION: Do NOT rotate the crankshaft clockwise to TDC, valve or piston damage could occur.

1. Timing chain over exhaust camshaft sprocket, around idler sprocket and around crankshaft sprocket.
2. Set camshaft sprockets at timed position and install timing chain. Remove timing pin from intake camshaft. Using J-39579, rotate the intake camshaft sprocket counterclockwise until timing chain can be installed over sprocket. Release J-39579 after timing chain has been installed over sprocket. The length of chain between intake and exhaust camshaft sprockets should tighten. The timing pin should easily fit through intake camshaft sprocket timing hole into timing chain housing timing hole. If timing pin does not fully index, the camshafts are NOT timed correctly and the procedure MUST be repeated.
3. With timing pins installed, raise and support vehicle.
4. With slack removed from timing chain between intake camshaft sprocket and crankshaft sprocket, timing marks on crankshaft and engine block should be aligned. If the marks are not aligned, move timing chain one tooth forward or rearward to align marks. Remove slack and recheck marks.
5. Reload tensioner assembly to zero position as follows:

• 1. Form a keeper out of heavy gauge wire into a U-shaped piece with a half inch opening.
  2. Apply slight force on tensioner blade to compress plunger.
  3. Insert small screwdriver into reset access hole and pry rachet pawl away from ratchet teeth while forcing the plunger completely in the hole.
  4. Install keeper between access hole and blade.

1. Tensioner assembly to chain housing and recheck plunger assembly installation, noting long end is toward crankshaft.
2. Tighten timing chain tensioner bolts to 10 Nm ( 89 in lbs ) .
3. Lower vehicle to point where timing pins can be removed from camshaft sprockets.
4. Rotate crankshaft two revolutions in the clockwise direction. Align crankshaft keyway with the mark on cylinder block and reinstall timing pins through camshaft sprockets into housing timing holes. Timing pins should slide easily through timing holes. If timing pins cannot be inserted easily, repeat procedure to properly time engine.

CAUTION: If the engine is not correctly timed, severe engine damage could occur.

1. Timing chain guides.
2. Engine front cover.
3. Negative battery cable.

Expert:	Dave Nova
Pos. Feedback:	99.2 %
Accepts:
Answered:	10/6/2008

ASE Certified Technician

20+ years experience. ASE Master and Advanced Level L1 Certification.GM World Class Certification