GM 17120070 Lifter,Valve

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To single out a noisy valve lifter at idle, use a hose length next to each valve and listen over the other end of the hose. Alternatively, remove the rocker arm cover and put fingers on valve spring retainers one by one while the engine is idling. If a faulty lash adjuster is present, it may be felt as the valve seats shock that often indicates trapped dirt in it. To do so first disconnect and ensure that there are no lockout features engaged if you have a Delco Loc II audio system and this is done by disconnection of the negative battery terminal. Remove rocker arm covers; loosen rocker arm nut and push rocker arm away from push rod as shown below: The next step is to take off the pushrod making sure to remove it carefully using a magnetic pick up tool or scribe in case removing any lash adjuster. For stuck lash adjusters, avoid damaging them from outside using a specialized hydraulic lash adjuster removal tool. In case you are going to remove several of them, keep them in a labeled container for reinstallation into their original positions. Cleaning the lash adjusters with solvent check for wear, scuffing, or uneven wear particularly on lash adjuster walls, pushrod seats, and foot. The base should slightly bulge outwards while concave ones indicate that both camshaft and lash adjusters require replacement. Examine lash adjuster bores in the engine block if lash adjuster walls are damaged or worn. Outer rollers should be free-rolling so they need to be checked (for roller lash adjusters). When replacing new lash adjusters, always get yourself another camshaft since used ones cannot be reused unless they are fixed back at their previous places together with the initial camshaft. Always ensure molybase grease or engine assembly lube has been applied on lash adjusters before installation then can proceed with other steps in reverse order.

For both the intake and exhaust parts, you should loosen the camshaft housing-to-cylinder head bolts in 1/4-turn increments, following the tightening sequence in reverse.

Common causes of noisy valve lifters include dirt trapped inside the lifter and issues related to oil flow, viscosity, or pressure.

Various methods can be used to extract the lifters from the bores, depending on the specific situation and available tools.

After removing the lifters, you should clean them and inspect them for scuffing, score marks, and uneven wear. Additionally, check the rollers for wear and damage. Replace the lifters if necessary.

After installing the camshaft, you should install the thrust plate and tighten the bolts. Reinstall the oil pump drive.

If any camshaft journal diameter falls below the specified value, it is necessary to replace the camshaft.