Hummer H3. Manual — part 407

Scored camshaft journals

Damaged camshaft lobes

Damaged camshaft sprocket locator slots

Damaged threads

3. Measure the camshaft lobes using a micrometer. The intake camshaft lobes should be a

minimum of 41.5 mm (1.635 in). The exhaust camshaft lobes should be a minimum of 41
mm (1.615 in).

Fig. 459: Measuring Camshaft Runout & Lobe Lift
Courtesy of GENERAL MOTORS CORP.

4. Use J 7872 to measure the camshaft runout.

1. Set the camshaft in V-blocks between the centers.

2. Measure the intermediate camshaft journal.

5. Use J 7872 to measure the camshaft lobe lift.

1. Lubricate the camshaft to V-block contact areas with engine oil.

2. Set the camshaft on V-blocks.

3. Measure the camshaft lobe lift.

2007 Hummer H3

2007 ENGINE Engine Mechanical - 3.7L - H3

6. If the runout or camshaft lobe lift is not within specifications, replace the camshaft.

TIMING CHAIN AND SPROCKETS CLEANING AND INSPECTION

Fig. 460: View Of Timing Chain & Sprockets
Courtesy of GENERAL MOTORS CORP.

1. Inspect the timing chain sprockets for cracks or teeth that are worn, broken or chipped.

2. Inspect the dowel pin for wear or damage.

3. Inspect the timing chain for binding or stretching.

2007 Hummer H3

2007 ENGINE Engine Mechanical - 3.7L - H3

4. Inspect the crankshaft sprocket keyway and locating dowel pin in the crankshaft for

damage.

5. Inspect the timing chain shoe and guide for excessive wear or cracks.

6. Inspect the timing chain tensioner for damage.

7. Replace the timing chain and sprockets if damaged.

VALVE ROCKER ARM AND VALVE LASH ADJUSTER CLEANING AND INSPECTION

Fig. 461: View Of Valve Rocker Arm
Courtesy of GENERAL MOTORS CORP.

1. Clean the valve rocker arms and valve lash adjusters in cleaning solvent.

2. Dry the valve rocker arms and valve lash adjusters with compressed air.

3. Inspect the valve rocker arms for the following conditions:

Excessive wear at the valve contact or valve lash adjuster socket area

2007 Hummer H3

2007 ENGINE Engine Mechanical - 3.7L - H3

A loose or damaged pin

A worn or damaged roller. The roller should rotate freely with no binding or
roughness.

Fig. 462: View Of Valve Lash Adjuster
Courtesy of GENERAL MOTORS CORP.

2007 Hummer H3

2007 ENGINE Engine Mechanical - 3.7L - H3