Hummer H2. Manual - part 68

Fig. 24: Typical Gear Timing Mark Alignment 

TIMING BELTS 

Cogged tooth belts are commonly used on overhead cam engines. Inspect belt teeth for rounded corners or 
cracking. Replace belt if it is cracked, damaged, missing teeth or oil soaked.  

Used timing belt must be installed in original direction of rotation. Inspect all sprocket teeth for wear. Replace 
all worn sprockets. Sprockets are marked for timing purposes. Engine is positioned so that crankshaft sprocket 
mark will be upward. Camshaft sprocket is aligned with reference mark on cylinder head or timing belt cover 
and then timing belt can be installed. See Fig. 25 . 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Engine Overhaul Procedures

  

Fig. 25: Typical Camshaft Belt Sprocket Alignment 

TENSION ADJUSTMENT 

If guide rails are used with spring loaded tensioners, ensure at least half of original rail thickness remains. 
Spring loaded tensioner should be inspected for damage.  

Ensure all timing marks are aligned. Adjust belt tension using manufacturer's recommendations. Belt tension 
may require checking using tension gauge. See Fig. 26 . 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Engine Overhaul Procedures

  

Fig. 26: Adjusting Typical Timing Belt Tension 

TIMING GEARS 

TIMING GEAR BACKLASH & RUNOUT 

On engines where camshaft gear operates directly on crankshaft gear, gear backlash and runout must be 
checked. To check backlash, install dial indicator with tip resting on tooth of camshaft gear. Rotate camshaft 
gear as far as possible. Adjust indicator to zero. Rotate camshaft gear in opposite direction as far as possible and 
note reading.  

To determine timing gear runout, mount dial indicator with tip resting on face edge of camshaft gear. Adjust 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Engine Overhaul Procedures

  

indicator to zero. Rotate camshaft gear 360 degrees and note reading. If backlash or runout exceeds 
specification, replace camshaft and/or crankshaft gear.  

REAR MAIN OIL SEAL INSTALLATION 

One-Piece Type Seal 

For one-piece type oil seal installation, coat block contact surface of seal with sealer if seal is not factory 
coated. Ensure seal surface is free of burrs. Lubricate seal lip with engine oil and press seal into place using 
proper oil seal installer. See Fig. 27 .  

Fig. 27: Installing Typical One-Piece Oil Seal 

Rope Type Seal 

For rope type rear main oil seal installation, press seal lightly into seat area. Using seal installer, fully seat seal 
in bearing cap or cylinder block.  

Trim seal ends even with cylinder block parting surface. Some applications require sealer to be applied on main 
bearing cap before installing. See Fig. 28 .  

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Engine Overhaul Procedures