GM 19301058 Bearing,Camshaft

For 4.5L and 4.9L engines, maintain valve lifter and pushrod order during removal and installation. Remove the intake manifold and valve covers to access lifters. "O" markings indicate oversize lifters. Reinstall associated components. For the 4.6L engine, start by removing the camshaft cover. Next, remove camshafts and lifters, storing lifters face-down for oil retention. Return lifters to original bores during installation, followed by camshafts and cover.

To determine cam lobe wear, you should first position the number one piston at TDC on the compression stroke. Then, loosen the rocker arm nuts and pivot the rocker arms sideways. Afterward, mount a dial indicator on the engine and position the plunger against the top of the first pushrod. Zero the dial indicator and slowly turn the crankshaft in the normal direction of rotation until the indicator needle stops and begins to move in the opposite direction. Record this figure and repeat the check for each valve.

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.