Chevrolet 14002525 Bearing, Camshaft

The last and most essential of camshaft tests is lobe lift which should be taken prior to the dismantling of the engine. Begin with the rocker arm cover(s) then pull the rocker arms and ball pivots away from the cylinder head(s). Secure a dial indicator on top such a way that the stem of the indicator leaning against the end of the exhaust valve pushrod while the plunger touching the pushrod. Turn the crankshaft slowly and get the Lash Adjuster on the bottom of the cam lobe which also gives the least height to the pushrod. Zero the dial-indicator, and after rotating the crank-shaft further, observe the maximum movement of the push-rod and the lobe lift indicated on the specification. Perform this to each of the remaining valves, noting that intake and exhaust valves may be standardized differently. Camshafts which are out of 0.002-inch of the specified lobe lift should be replaced with a new one. After the camshaft has been pulled out, wash the camshaft with solvent and examine the bearing journals for sign of wear, pitting, or seizure. When the journals are bad, both the camshaft and bearings will have to be replaced. Place a dial indicator on each camshaft bearing journal and record the inside diameter of each and record two readings on each bearing. Measure the bearing journals with a micrometer, to check the bearing for excessive wear or out-of-roundness; if the bearings are more than 0.001-inch out-of-round, replace the camshaft. Inspect the camshaft lobes for such things as discolouration, scoring and uneven wear; if these are okay and the lobe lift measurements were as laid down the camshaft can be used time again. Thoroughly wash out the Lash Adjusters and visually check each one for scuffing, score marks and worn areas; if any of the Lash Adjuster feet are concave, all the Lash Adjusters should be replaced. If new Lash Adjusters have been added, a new camshaft must be run as well, and never run previously used Lash Adjusters if the old camshaft is not installed in its locations. Camshaft bearing sleeves are fairly tough to install or replace due to the size and the fact that you need special tools and skills to work on them - it is better to drop the block to an automotive machine shop.

After removing the camshaft from the engine, clean it with solvent and dry it, then inspect the bearing journals for uneven wear, pitting, and signs of seizure; if damaged, both the camshaft and bearings need replacement. Measure the bearing journals with a micrometer to check for excessive wear or out-of-round conditions, replacing the camshaft if it exceeds 0.001-inch out-of-round. Examine the camshaft lobes for heat discoloration, score marks, chipped areas, pitting, and uneven wear; if the lobes are in good condition and the lobe lift measurements are within specified limits, the camshaft may still be usable. For Lash Adjusters that have been sticking due to sludge and varnish buildup, clean them thoroughly without mixing them up, ensuring they are reinstalled in their original locations. Inspect each Lash Adjuster for scoring and galling, checking the pushrod seat and heel for wear; if any Lash Adjuster heel is concave or if the bottom of any Lash Adjuster shows excessive wear, replace the entire set. If conventional valve Lash Adjusters require replacement, install a new camshaft as well; roller type Lash Adjusters can be reused with a new camshaft. Worn Lash Adjusters should be replaced as internal components are not sold separately, although cleaning may restore functionality. To dismantle a valve Lash Adjuster, hold the plunger down and extract the retainer ring, then remove the pushrod seat and oil metering valve, followed by the plunger, check ball, and spring. Clean all components with solvent and inspect for wear, ensuring that a contaminated Lash Adjuster can operate properly after reassembly. If a Lash Adjuster is worn out, replace it and clean any sealer coating from new Lash Adjusters before reassembly, which involves placing the check ball, inserting the spring and retainer, and filling the assembly with oil before installing the metering valve and pushrod seat. When reinstalling Lash Adjusters, ensure they are placed in their original bores with oiling orifices facing the front of the engine, and coat each Lash Adjuster with moly-base grease or engine assembly lube. Camshaft bearing replacement requires special tools and expertise, so it is advisable to take the block to an automotive machine shop for proper handling.

Clean any dirt, oil, or old gasket material from the camshaft rear cover, then apply a 1/8-in (3 mm) diameter bead of RTV or equivalent sealant around the sealing surface before bolting the cover to the engine block.

To extract the camshaft, assemble a puller with the appropriate components, such as the puller screw, expanding collet, and back-up nut. Insert this assembly into the camshaft bearing for removal. Repeat this process for each bearing, except the front one, which can be extracted using a spacer.

Mount the camshaft on V-blocks and use a dial gauge to measure lobe lift and run-out, rejecting any that do not meet specified limits.

Reposition the piston at TDC and repeat the check for the remaining valves, ensuring each piston is at TDC in firing order, turning the crankshaft 180 degrees between cylinders.

Store lifters in a segregated box to maintain their positions for reinstallation.

The bearing surfaces and the surfaces of the cam lobes should be examined.

Reject any camshaft that does not meet specified limits.

Remove the two camshaft thrust plate screws by working through the holes in the camshaft gear.

Shallow surface scratches can be removed with fine emery cloth or an oil stone.

After installing the new bearings, install a new camshaft rear expansion plug flush with the rear surface of the block, then reinstall the flywheel and oil pan.