1. Valve Clearance Adjustment
Valve Lash Adjustment
Tools Required
J 26900-1 Outside Micrometer
Important:
* Valve clearance measurement should only be done on a cold engine.
* To change the valve clearance on a given valve, the lifter must be replaced by one that is thicker or thinner in size.
* Lifters are available in 35 different sizes, in increments of 0.020 mm (0.0008 in).
* Lifters range in size from 5.060 mm (0.1992 in) to 5.740 mm (0.2260 in).
Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.
For Vehicles equipped with OnStar (RPO UE1) with Back Up Battery:
The Back Up Battery is a redundant power supply to allow limited OnStar functionality in the event of a main vehicle battery power disruption to the VCIM (OnStar module). Do not disconnect the main vehicle battery or remove the OnStar fuse with the ignition key in any position other than OFF. Retained accessory power (RAP) should be allowed to time out or be disabled (simply opening the driver door should disable RAP) before disconnecting power. Disconnecting power to the OnStar module in any way while the ignition is On or with RAP activated may cause activation of the OnStar Back-Up Battery (BUB) system and will discharge and permanently damage the back-up battery. Once the Back-Up Battery is activated it will stay on until it has completely discharged. The BUB is not rechargeable and once activated the BUB must be replaced.
1. Disconnect the negative battery cable.
2. Remove the cylinder head cover. Service and Repair
3. Turn the crankshaft clockwise until the alignment notch on the crankshaft pulley is aligned with the "0" mark on the engine front cover tab.
4. Check that the point marks on the camshaft gears are aligned. If the point marks on the camshaft gears are not aligned, turn the crankshaft clockwise one revolution in order to align the camshaft gears.
5. Using a feeler gage, measure the clearance between the intake valve lifters and the intake camshaft for cylinders #1, and #2.
0.15-0.25 mm (0.006-0.010 in)
Important: Record any out of specification valve clearance measurements. The measurements will be used later to determine the required replacement lifter.
6. Using a feeler gage, measure the clearance between the exhaust valve lifters and the exhaust camshaft for cylinders #1, and #3.
0.25-0.35 mm (0.010-0.014 in)
Important: Record any out of specification valve clearance measurements. The measurements will be used later to determine the required replacement lifter.
7. Turn the crankshaft clockwise 1 revolution until the alignment notch on the crankshaft pulley is aligned with the "0" mark on the engine front cover tab.
8. Using a feeler gage, measure the clearance between the intake valve lifters and the intake camshaft for cylinders #3, and #4.
0.15-0.25 mm (0.006-0.010 in)
Important: Record any out of specification valve clearance measurements. The measurements will be used later to determine the required replacement lifter.
9. Using a feeler gage, measure the clearance between the exhaust valve lifters and the exhaust camshaft for cylinders #2, and #4.
0.25-0.35 mm (0.010-0.014 in)
Important: Record any out of specification valve clearance measurements. The measurements will be used later to determine the required replacement lifter.
10. If there were any valve clearances that were out of specifications, the camshaft(s) must be removed in order to replace the lifter(s). To remove the intake camshaft, refer to Intake Camshaft and Valve Lifter Replacement or to remove the exhaust camshaft, refer to Exhaust Camshaft and Valve Lifter Replacement. Service and Repair
Lifter Selection
Important: In order to maintain the specified valve clearance the proper lifter must be selected. Perform the following procedure in order to select the proper lifter:
1. Determine the valve(s) clearances that were out of specifications.
2. Remove the lifter(s) from the lifter bores of the out of specification valves.
3. Use a J 26900-1 to measure the thickness of the removed lifter.
4. After measuring the lifter, refer to the record of the out of specification valve clearances.
5. After determining the two measurements, select the proper lifter thickness for the required valve clearance.
6. After selecting the proper lifter, the camshaft must be re-installed and the valve clearance re-measured.
7. After confirming the valve clearance is correct for all valves, re-assemble the timing chain and timing chain housing. Refer to the installation instructions in Timing Chain and Sprocket Replacement (Timing Chain and Sprocket Replacement).
8. Install the cylinder head cover. Service and Repair
Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
9. Connect the negative battery cable.
Tighten the bolt to 15 N.m (11 lb ft).