Hummer H3. Manual — part 306

Fig. 92: Loosening Camshaft Sprocket Bolt
Courtesy of GENERAL MOTORS CORP.

36. Before performing one of the top dead center (TDC) procedures, break loose both the

exhaust and intake camshaft sprocket bolts. Use a 25 mm (1 in) open end wrench on the
camshaft hexes to hold the camshaft from turning. DO NOT remove the bolts.

37. Perform one of the following methods for the service timing procedure.

2007 Hummer H3

2007 ENGINE Engine Mechanical - 3.7L - H3

Fig. 93: Rotating Engine To TDC
Courtesy of GENERAL MOTORS CORP.

38. First Method-Rotate the engine clockwise by hand to TDC on the compression stroke by

using a piston TDC indicator tool and/or dial indicator in the number 1 cylinder.

2007 Hummer H3

2007 ENGINE Engine Mechanical - 3.7L - H3

Fig. 94: View Of TDC Indicator Tool
Courtesy of GENERAL MOTORS CORP.

39. First Method (continued) - The TDC indicator tool graduation marks on the shaft should

note top of the piston stroke.

2007 Hummer H3

2007 ENGINE Engine Mechanical - 3.7L - H3

Fig. 95: Checking For TDC Position
Courtesy of GENERAL MOTORS CORP.

40. First Method (continued) - When the piston is at TDC, the flats at the rear of the camshafts

will be facing up and level when using a straight edge across the camshaft flats.

2007 Hummer H3

2007 ENGINE Engine Mechanical - 3.7L - H3