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