Camshafts Cleaning and Inspection

Tools Required

• J 26900-2  Outside Micrometer. See Special Tools and Equipment .
• J 8001  Dial Indicator Set. See Special Tools and Equipment .
• J 26900-13  Magnetic Indicator Base. See Special Tools and Equipment .

Fig 1: Camshaft Journals And Lobes
Courtesy of GENERAL MOTORS CORP.
1. Inspect the camshaft journals and lobes for wear or scoring (1, 2).
2. Wash the cylinder head in solvent.
3. Inspect the cylinder head for cracks or other signs of damage.
4. Inspect the camshaft bearing caps for wear, cracks and scoring.
5. Inspect the camshaft bearing journals in the cylinder head for wear, cracks and scoring.
6. If excessive wear or scoring is present, or if the cylinder head is cracked, replace the cylinder head (with bearing caps).
Fig 2: Measuring Camshaft Lobe Height
Courtesy of GENERAL MOTORS CORP.
7. Measure the camshaft lobe height using the J 26900-2  . See Special Tools and Equipment . Replace the camshaft if any lobe is below the minimum.

   Standard Intake Camshaft Lobe No. 1 Height:  40.607-40.707 mm (1.5958-1.5997 in)

   Standard Intake Camshaft Lobe No. 2 Height:  38.769-38.869 mm (1.52362-1.52755 in)

   Minimum Intake Camshaft Lobe No. 1 Height:  40.45 mm (1.5925 in)

   Minimum Intake Camshaft Lobe No. 2 Height:  38.61 mm (1.5201 in)

   Standard Exhaust Camshaft Lobe No. 1 Lobe Height:  40.019-40.119 mm (1.57275-1.57668 in)

   Standard Exhaust Camshaft Lobe No. 2 Lobe Height:  38.863-38.963 mm (1.52732-1.53125 in)

   Minimum Exhaust Camshaft Lobe No. 1 Height:  39.86 mm (1.5693 in)

   Minimum Exhaust Camshaft Lobe No. 2 Height:  38.71 mm (1.5240 in)

Fig 3: Dial Indicator Set And Magnetic Base
Courtesy of GENERAL MOTORS CORP.
8. Place the camshaft (1) onto V-blocks. Measure the camshaft runout using the J 8001  with the J 26900-13  . See Special Tools and Equipment . Replace the camshaft if the runout exceeds specifications.

   Camshaft Runout:  0.03 mm (0.0012 in)

9. Clean the journals of the camshaft and the cylinder head.
10. Do not install the valve lifters.
Fig 4: Camshaft Bearing Cap Bolts
Courtesy of GENERAL MOTORS CORP.
11. Install the camshafts.
IMPORTANT: Do not turn the camshafts while the gauging plastic is installed.
12. Place a piece of gauging plastic across the full width of each camshaft journal.
IMPORTANT: Cylinder head and camshaft damage may result if the bearing caps are incorrectly installed. The oil clearance measurement will also be incorrect.
13. Install the camshaft bearing caps in their original locations.
NOTE: Refer to Fastener Notice in Cautions and Notices.
14. Use 3 progressive steps to tighten the camshaft bearing cap bolts in sequence.

    Tighten:  Tighten the bolts to 18.5 N.m (14 lb ft).

15. Remove the camshaft bearing caps.
16. Measure the gauging plastic at its widest point.

    Standard Oil Clearance, No. 1 Camshaft Cap:  0.035-0.076 mm (0.0014-0.0030 in)

    Standard Oil Clearance, No. 2-5 Camshaft Caps:  0.035-0.072 mm (0.0014-0.0028 in)

    Maximum Oil Clearance:  0.10 mm (0.0039 in)

17. If the oil clearance is greater than the maximum, replace the camshaft. If necessary, replace the cylinder head with caps as a set.
18. Install the camshafts.
19. Using the J 8001  , measure the thrust clearance while moving the camshaft back and forth. See Special Tools and Equipment .

    Standard Thrust Clearance:  0.04-0.14 mm (0.0016-0.0055 in)

    Maximum Thrust Clearance:  0.15 mm (0.0059 in)

20. If the thrust clearance is greater than maximum, replace the camshaft. If necessary, replace the bearing caps and cylinder head as a set.