GM 17120070 Lifter,Valve

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A noisy valve lifter can be isolated during idling by using a length of hose near each valve and listening at the hose's other end. Another method is to remove the rocker arm cover and place a finger on each valve spring retainer, one at a time, while the engine idles. If a defective lash adjuster is present, the shock felt as the valve seats will reveal it, often caused by trapped dirt inside the lash adjuster. To address this, begin by disconnecting the negative battery terminal, ensuring that any lockout feature is disabled if the vehicle has a Delco Loc If audio system. Remove the rocker arm cover, loosen the rocker arm nut, and rotate the rocker arm away from the pushrod. Remove the pushrod, and carefully extract the lash adjuster using a magnetic pick-up tool or scribe. For stuck lash adjusters, use a specialized hydraulic lash adjuster removal tool, avoiding external damage to the lash adjuster body. If removing multiple lash adjusters, store them in a labeled container to return them to their original positions. Clean the lash adjusters with solvent, checking for wear, scuffing, or uneven wear on the lash adjuster walls, pushrod seats, and foot. The lash adjuster foot should be slightly convex, and concave bases indicate a need for lash adjuster and camshaft replacement. Examine lash adjuster bores in the engine block if lash adjuster walls are damaged or worn. For roller lash adjusters, inspect rollers for wear and ensure they turn freely. When installing new lash adjusters, a new camshaft is required; never use used lash adjusters unless they can be placed back in their original locations with the original camshaft. Ensure the lash adjusters are coated with moly-base grease or engine assembly lube during installation, and then proceed with the remaining 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.