GMC 12721201 LIFTER ASM-VLV

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To do this, the operator requires special tools. Removing the timing chain and sprockets entail unplugging the negative battery cable. The subsequent steps are taking out the timing chain housing-to-camshaft housing bolts, removing the ignition coil and module assembly, and disconnecting an Idle speed power steering pressure switch. The power steering pump as well as brackets need to be removed first then followed by removal of power steering pump drive pulley. Remove oil/air separator as an assembly with hoses attached, then remove fuel rail from cylinder head. At rear for exhaust, unplug oil pressure sending unit wire and unbolt engine lifting bracket. Both intake and exhaust: Loosen camshaft housing-to-cylinder head bolts in 1/4-turn increments while reversing tightening sequence. Remove housing from cylinder head and then remove camshaft cover as well as housing bolts. Very gently lift the camshaft out of the housing. Remove old gasket material, clean surfaces. Pull oil seal from intake camshaft. Remove lash adjusters keeping them organized. Inspect lash adjusters visually; measure bore, check lash adjuster diameters anyway. When installing new gasket, position camshaft housing with lubricated components in it followed by installation of lash adjusters and lubricating lip on oil seal (intake cam). Install cam shaft up in its bearing with dowel pin UP in front sprocket hole on gear side of engine block! Apply pipe sealant to bolt threads, install new housing seals, install cam shaft cover with bolts making sure that oil seal depth does not exceed 0.020 inches from outside face of end cap or bearing holder flange that provides a leak-free joint between two components; tighten these down in order specified by manufacturer's instructions until tightened properly according specifications listed under "tightening torque" section of their website; make certain there is no excess around edges which could cause damage during handling process or while being installed onto other parts such as valve cover gasket's edge. Power steering pump pulley must be installed again along with all other parts previously removed before this can happen, so don't forget about changing oil filter first too! If you are installing new lash adjusters or are experiencing lash adjuster noise, follow a bleed procedure to warm up the engine and increase the engine speed until the noise goes away. Road-test vehicle and check for leaks.

There are various methods that can be employed to diagnose a noisy Lash Adjuster. To start with, you can listen at the other side near the valve locations using a mechanic's stethoscope or a length of hose while the engine is idling in order to locate a noisy Lash Adjuster. Another way involves removal of the rocker arm cover and touching each valve spring retainer one at a time with an idling engine. If one of the Lash Adjusters is bad, you will feel a noticeable shock in the retainer every time the valve seats. Some common causes for noisy Lash Adjusters include dirt in the Lash Adjuster and problems related to oil flow, viscosity or pressure. There are few things that need to be done before making any conclusions about the problematic Lash Adjusters. Firstly, it is necessary to inspect the engine oil for fuel contamination; ensure that it's at proper level; clean and with proper viscosity. For removal, start by removing intake manifold and rocker arm cover(s). After that remove rocker arms and pushrods. If your engine has roller Lash Adjusters (1994 and newer models), also remove lifter guide. Different methods can be used to get out the Lash Adjusters from their bores. However, in some cases, you may not have to use this special tool made for this purpose. In newer engines without significant varnish buildup, Lash Adjusters can often be removed using a small magnet or even your fingers. Use a machinist's scribe with one end bent as an alternative method of pulling them out by placing its point under the retainer ring on top of each Lash Adjuster. Lash Adjuster removal should avoid using pliers unless they will be replaced as pliers can damage precision machined and hardened Lash Adjusters.Try not to forget that before removing them carefully place them in a well labeled container to make sure that they are reinstalled in their original positions later on since some engines may have both standard and 0.010-inch oversize Lash Adjusters installed at the factory, which are marked by a drop of white paint and a 0.25 (mm) OS stamp on them. As for inspection and installation, you should remember that Lash Adjuster parts cannot be sold separately. The Lash Adjusters have to be replaced with new ones if they are worn out; in case you have conventional Lash Adjusters in your engine, camshaft should also be replaced. It is important never to mix used conventional Lash Adjusters with a new camshaft or new conventional Lash Adjusters with a used camshaft. Nevertheless, used roller Lash Adjusters can be reinstalled with a new camshaft, and the original camshaft can be used if new roller Lash Adjusters are installed provided that the used parts are in good condition. Whenever you are reinstalling used Lash Adjusters ensure that they are put back to their original bores, soak new Lash Adjusters in oil to release any air pockets trapped within them, also coat all Lash Adjuster bottoms with moly-base grease or engine assembly lube prior to installing them. Remaining installation steps must now be done in reverse order while for those installing roller Lash Adjusters make sure the lifter guide bolts are properly tightened. Lastly start up the engine and look out for any oil leaks.

When installing new lifters:A new camshaft is required when installing new lifters; never use used lifters unless they can be placed back in their original locations with the original camshaft.Ensure the lifters are coated with moly-base grease or engine assembly lube during installation.Proceed with the remaining steps in reverse order to complete the lifter replacement process.

To determine the extent of cam lobe wear, position the number one piston at TDC on the compression stroke, remove the valve cover, and loosen the rocker arm nuts to access the pushrods. Then, mount a dial indicator on the engine, position the plunger against the top of the first pushrod, and zero the dial indicator. Slowly turn the crankshaft in the normal direction of rotation until the indicator needle stops and moves in the opposite direction, indicating maximum cam lobe lift. Record this figure and repeat the check for each valve.

For installation, the camshaft bearing journals and cam lobes should be lubricated with camshaft and lifter assembly lube.

If the lobes are in good condition and the measurements are as specified, the camshaft can be reused.

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.