Hummer 12721203 LIFTER ASM-VLV

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Check the rocker arm pivot support pedestal for cracks and other obvious damage.

Remove the bolts and camshaft retainer plate, noting the orientation. Thread three long bolts into the camshaft sprocket bolt holes to assist in removal. Carefully pull the camshaft out, supporting it near the block to prevent damage to the bearings.

Install the balancer shaft drive gear, ensuring proper alignment of timing marks. Install the timing chain and sprockets, lubricate the lifters with clean engine oil, and reinstall them in their original locations if applicable.

The most common cause of noise is dirt trapped between the plunger and lifter body.

Rotate the crankshaft 60 degrees counterclockwise to prevent the valves from possibly hitting the pistons.

To check for a noisy valve lifter, you can use a mechanics stethoscope or a length of hose near each valve while listening for excessive clearance in the valvetrain. If a lifter is defective, it will be evident from the noise.

The hydraulic lash adjusters can be lifted from the cylinder head, ensuring that any reused components are placed back in their original positions.

Before starting the engine after camshaft installation, it is essential to change the oil and install a new oil filter.

If the cam lobe lift is less than the specified value, it is recommended to install a new camshaft.

Begin by removing the intake manifold or supercharger, valve covers, rocker arms, pushrods, timing chain, timing chain tensioner, cylinder heads, oil pan, oil pump, oil deflector, radiator, air conditioning condenser, and the Camshaft Position sensors.

Measure the camshaft lobe height and base circle to determine lobe lift, recording the figures for future reference.

Check the camshaft caps for markings and mark them with paint if necessary before removal.

The factory-recommended procedure involves several steps, including the removal of the engine, which can simplify the process, although it is not absolutely necessary.

If the lobe lift is below specifications, a new camshaft should be installed.

Remove the bolts and the camshaft retainer plate, noting the orientation. Thread a bolt into the camshaft sprocket bolt hole to assist in removal. Carefully pull the camshaft out, supporting it near the block to prevent damage to the bearings.

Before starting the engine, change the oil and install a new oil filter.

A noisy valve lifter can be isolated when the engine is idling by using a mechanic's stethoscope or a length of hose near each valve while listening at the other end. Alternatively, you can remove the valve cover and touch each valve spring retainer with the engine idling to feel for shock if a lifter is defective.

Clean the lifters and check for scuffing, score marks, and uneven wear. If the lifters are worn or damaged, it's advisable to replace them along with the camshaft. For roller lifters, also check the rollers for wear and damage.

A noisy valve lifter can be isolated when the engine is idling by using a mechanic's stethoscope or a length of hose near each valve while listening at the other end. Alternatively, you can remove the valve cover and touch each valve spring retainer with the engine idling to feel for shock if a lifter is defective.

Before installing the camshaft, you should lubricate the camshaft bearing journals and lobes with assembly lube.

Compare the camshaft lobe heights by measuring each lobe with a micrometer, recording the measurements for both intake and exhaust lobes separately; if the difference exceeds 0.005 inch, the camshaft should be replaced.

Arrange to store the lifters in a clearly labeled box to ensure they are reinstalled in their original locations.

Before removing the camshaft, the radiator, auxiliary automatic transmission fluid cooler (if equipped), power steering cooler, air conditioning condenser, valve covers, intake manifold, rocker arms, pushrods, timing chain and sprockets, and cylinder heads need to be removed.

If the cam lobe lift is less than specified, you should install a new camshaft.

The steps to remove the camshaft are as follows: 1. Remove the intake manifold. 2. Remove the rocker arms. 3. Remove the pushrods. 4. Remove the timing chain. 5. Remove the camshaft sprocket. 6. Remove the balance shaft drive gear. 7. Remove the fan, radiator, and condenser. 8. Store the lifters in a labeled box. 9. Remove the lifter retainer. 10. Extract the lifters from the bores using a special tool, magnet, or your fingers. 11. Remove the camshaft retainer plate. 12. Use three 6-inch long, 5/16-18 bolts as a handle to remove the camshaft from the block.

Yes, used roller lifters can be reinstalled with a new camshaft, while original camshafts can be reused with new roller lifters.

Before removing the camshaft, the radiator, auxiliary automatic transmission fluid cooler (if equipped), power steering cooler, air conditioning condenser, valve covers, intake manifold, rocker arms, pushrods, timing chain and sprockets, and cylinder heads need to be removed.

It is important to keep all lifters separated and identified for reinstallation. After cleaning each lifter individually, inspect for any nicks or gauges, as any damage necessitates replacement.

After installing the camshaft, you should:1. Refill the cooling system.2. Change the engine oil and filter.3. Start the engine and check for leaks.

Proper labeling and storage of the lifters are essential to ensure that they are returned to their original locations during reinstallation, preventing any mix-up.

The initial steps for checking camshaft lobe lift before removal involve removing the valve covers and loosening the rocker arm nuts to pivot the rocker arms for access to the pushrods. A dial indicator should be mounted on the engine, positioned directly above the first pushrod.

After installing the camshaft, the cooling system should be refilled, the oil should be changed, and a new oil filter should be installed before starting and running the engine.

The steps for installing the camshaft are as follows: 1. Lubricate the camshaft bearing journals and cam lobes with assembly lube. 2. Slide the camshaft into the engine. 3. Install the camshaft thrust plate. 4. Install the balance shaft drive gear. 5. Install the timing chain and sprockets. 6. Lubricate the lifters with clean engine oil. 7. Install the lifters in the block. 8. Complete the installation in reverse order of removal.

To install the camshaft into the engine, slide the camshaft carefully into place.

Proper labeling and storage of the lifters are essential to ensure that they are returned to their original locations during reinstallation, preventing any mix-up.

Lubricate the lifters with clean engine oil and install them in the retainers, ensuring proper alignment. Tighten the lifter retainer bolts to the specified torque.

Lifters can be extracted using a special tool, a small magnet, or a machinist's scribe. Caution is advised against using pliers unless replacing the lifters, as they may damage them.

Install new housing seals, the camshaft cover, and bolts while ensuring the oil seal is installed to the correct depth. Tighten the bolts in the specified sequence to the required torque and angle of rotation.

The procedure is essentially the same, but there is no pushrod cover to remove in this case.

Parts for valve lifters are not sold separately, and the effort to remove them again if repairs fail outweighs potential savings.

When installing the camshaft, exercise care to avoid damaging the seal, and coat the camshaft lobes and journals with moly-base grease or engine assembly lube prior to installation, ensuring the arrow on the thrust plate points up.