Hummer H2. Manual — part 65

Fig. 15: Checking Piston Ring End Gap

For checking side clearance, install rings on piston. Using feeler gauge, measure clearance between piston ring
and piston ring land. Check side clearance in several areas around piston. Side clearance must be within
specification.

If side clearance is excessive, piston ring grooves can be machined to accept oversize piston rings (if available).
Normal practice is to replace piston.

PISTON & CONNECTING ROD INSTALLATION

Cylinders must be honed prior to piston installation. See CYLINDER HONING under CYLINDER BLOCK.

Install upper connecting rod bearings. Lubricate upper bearings with engine oil. Install lower bearings in rod
caps. Ensure bearing tabs are properly seated. Position piston ring gaps according to manufacturer's
recommendations. See Fig. 16 . Lubricate pistons, rings and cylinder walls.

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Engine Overhaul Procedures

Fig. 16: Positioning Typical Piston Ring End Gap

Install ring compressor. Use care not to rotate piston rings. Compress rings with ring compressor. Install plastic
tubing protectors over connecting rod bolts. Install piston and connecting rod assembly. Ensure piston notch,
arrow or FRONT mark is toward front of engine. See Fig. 17 .

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Engine Overhaul Procedures

Fig. 17: Installing Piston & Connecting Rod Assembly

Carefully tap piston into cylinder until rod bearing is seated on crankshaft journal. Remove protectors. Install
rod cap and bearing. Lightly tighten connecting rod bolts. Repeat procedure for remaining cylinders. Check
bearing clearance. See MAIN & CONNECTING ROD BEARING CLEARANCE .

Once clearance is checked, lubricate journals and bearings. Install bearing caps. Ensure marks are aligned on
connecting rod and cap. Tighten rod nuts or bolts to specification. Ensure rod moves freely on crankshaft.
Check connecting rod side clearance. See CONNECTING ROD SIDE CLEARANCE .

CONNECTING ROD SIDE CLEARANCE

Position connecting rod toward one side of crankshaft as far as possible. Using feeler gauge, measure clearance
between side of connecting rod and crankshaft. See Fig. 18 . Clearance must be within specification.

Check for improper bearing installation, wrong bearing cap or insufficient bearing clearance if side clearance is
insufficient. Connecting rod may require machining to obtain proper clearance. Excessive clearance usually
indicates excessive wear at crankshaft. Crankshaft must be repaired or replaced.

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Engine Overhaul Procedures

Fig. 18: Measuring Connecting Rod Side Clearance

MAIN & CONNECTING ROD BEARING CLEARANCE

Plastigage Method

Plastigage method may be used to determine bearing clearance. Plastigage can be used with an engine in service
or during reassembly. Plastigage material is oil soluble.

Ensure journals and bearings are free of oil or solvent. Oil or solvent will dissolve material and false reading
will be obtained. Install small piece of Plastigage along full length of bearing journal. Install bearing cap in
original location. Tighten bolts to specification.

Remove bearing cap. Compare Plastigage width with scale on Plastigage container to determine bearing
clearance. See Fig. 19 . Rotate crankshaft 90 degrees. Repeat procedure. This is done to check journal
eccentricity. This procedure can be used to check oil clearance on both connecting rod and main bearings.

CAUTION: DO NOT rotate crankshaft while Plastigage is installed. Bearing clearance

will not be obtained if crankshaft is rotated.

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Engine Overhaul Procedures