Hummer H2. Manual — part 66

Fig. 19: Measuring Bearing Clearance

Micrometer & Telescopic Gauge Method

A micrometer is used to determine journal diameter, taper and out-of-round dimensions of the crankshaft. See
CLEANING & INSPECTION under CRANKSHAFT & MAIN BEARINGS in this article.

With crankshaft removed, install bearings and caps in original location on cylinder block. Tighten bolts to
specification. On connecting rods, install bearings and caps on connecting rods. Install proper connecting rod
cap on corresponding rod. Ensure bearing cap is installed in original location. Tighten bolts to specification.

Using a telescopic gauge and micrometer or inside micrometer, measure inside diameter of connecting rod and
main bearings bores. Subtract each crankshaft journal diameter from the corresponding inside bearing bore
diameter. This is the bearing clearance.

CRANKSHAFT & MAIN BEARINGS

REMOVAL

Ensure all main bearing caps are marked for location on cylinder block. Some main bearing caps have an arrow
stamped on them. The arrow must face timing belt or timing chain end of engine. Remove main bearing cap
bolts. Remove main bearing caps. Carefully remove crankshaft. Use care not to bind crankshaft in cylinder
block during removal.

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Engine Overhaul Procedures

CLEANING & INSPECTION

Thoroughly clean crankshaft using solvent. Dry with compressed air. Ensure all oil passages are clear and free
of sludge, rust, dirt and metal chips.

Inspect crankshaft for scoring and nicks. Inspect crankshaft for cracks using Magnaflux procedure. Inspect rear
seal area for grooving or damage. Inspect bolt hole threads for damage. If pilot bearing or bushing is used,
check pilot bearing or bushing fit in crankshaft. Inspect crankshaft gear for damaged or cracked teeth. Replace
gear if damaged. Ensure oil passage plugs are tight (if equipped).

Using micrometer, measure all journals in 4 areas to determine journal taper, out-of-round and undersize. See
Fig. 20 . Some crankshafts can be reground to the next largest undersize, depending on the amount of wear or
damage. Crankshafts with rolled fillet cannot be reground and must be replaced.

Fig. 20: Measuring Crankshaft Journals

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Engine Overhaul Procedures

Crankshaft journal runout should be checked. Install crankshaft in "V" blocks or bench center. Position dial
indicator with tip resting on the main bearing journal area. See Fig. 21 . Rotate crankshaft and note reading.
Journal runout must not exceed specification. Repeat procedure on all main bearing journals. Crankshaft must
be replaced if runout exceeds specification.

Fig. 21: Measuring Crankshaft Main Bearing Journal Runout

INSTALLATION

Install upper main bearing in cylinder block. Ensure lock tab is properly located in cylinder block. Install
bearings in main bearing caps. Ensure all oil passages are aligned. Install rear seal (if removed).

Ensure crankshaft journals are clean. Lubricate upper main bearings with clean engine oil. Carefully install
crankshaft. Check each main bearing clearance using Plastigage method. See MAIN & CONNECTING ROD
BEARING CLEARANCE .

Once clearance is checked, lubricate lower main bearing and journals. Install main bearing caps in original
location. Install rear seal in rear main bearing cap (if removed). Some rear main bearing caps require sealant to
be applied in corners to prevent oil leakage.

Install and tighten all bolts except thrust bearing cap to specification. Tighten thrust bearing cap bolts finger
tight only. Some models require that thrust bearing be aligned. On most applications, crankshaft must be moved
rearward then forward. Procedure may vary with manufacturer. Thrust bearing cap is then tightened to
specification. Ensure crankshaft rotates freely. Crankshaft end play should be checked. See CRANKSHAFT
END PLAY .

CRANKSHAFT END PLAY

Dial Indicator Method

Crankshaft end play can be checked using dial indicator. Mount dial indicator on rear of cylinder block.
Position dial indicator tip against rear of crankshaft. Ensure tip is resting against flat surface.

Pry crankshaft rearward. Adjust dial indicator to zero. Pry crankshaft forward and note reading. Crankshaft end

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Engine Overhaul Procedures

play must be within specification. If end play is not within specification, check for faulty thrust bearing
installation or worn crankshaft. Some applications offer oversize thrust bearings.

Feeler Gauge Method

Crankshaft end play can be checked using feeler gauge. Pry crankshaft rearward. Pry crankshaft forward. Using
feeler gauge, measure clearance between crankshaft and thrust bearing surface. See Fig. 22 .

Fig. 22: Checking Crankshaft End Play

Crankshaft end play must be within specification. If end play is not within specification, check for faulty thrust
bearing installation or worn crankshaft. Some applications offer oversize thrust bearings.

CYLINDER BLOCK

Block Cleaning

Only cast cylinder blocks should be hot tank cleaned. Aluminum cylinder blocks should be cleaned using cold
tank method. Cylinder block is cleaned in order to remove carbon deposits, gasket residue and water jacket
scale. Remove oil gallery plugs, freeze plugs and cam bearings before cleaning block.

Block Inspection

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Engine Overhaul Procedures