GMC 12453171 Bearing,Camshaft

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Before removing the camshaft, test the lobe lift to verify how much wear has occurred on the cam lobes. First, set number one piston at TDC on compression stroke. Then loosen rocker arm nuts and pivot the arms sideways. Thereafter fit a dial indicator over the engine, and set its stem touching top of first pushrod. Zero 0 Dial Indicator as well as slowly rotate crankshaft in normal direction until needle of indicator stops and begins to move in opposite way. Record this reading then replicate for every other valve. Where the maximum value of cam lobe lift is below that specified, install a new camshaft. Take off the intake manifold, rocker arms, push rods, timing chain and cam sprocket from the head prior to removing it from cylinder block; unfasten balancer shaft drive and driven gears if any; draw out camshaft very cautiously holding it at near block area; after removal look up bearing journals if they were worn out or damaged; inspect with micrometer bearing surfaces for increased clearances or ovality conditions; also review cams for discoloration as well as scoring marks being present; wash out lash adjusters and verify them under light projections or even examining several pittings or variable wear patterns; take off old gear roller followers too when replacing lobes including wipers along with it only; check rollers on roller type Lash Adjusters for wear/scoring/any damage that might be noticed therefrom/moly based grease/lube oil between lobes besides journals/insert nozzle into a hole (where not abraded), which must be careful at all costs not to scrape groove bearings. Next Lubricate all journals both lateral zones plus lopes with molly base greases or assembly compounds intended strictly for engines respectively: insert executive's element without scratching related beds but before enjoying harmonic aspect together by looking whether matching bones actually are still available plus need refitting them again: finally, oil changes should chiefly concern replacement of filters too then engine run on.

It is important to keep the valve lifters and pushrods in order during the removal and installation of the 4.5L and 4.9L engines.

To remove the camshaft, you should first remove the intake manifold, rocker arms, pushrods, timing chain, and camshaft sprocket. If applicable, also remove the balancer shaft drive and driven gears. Carefully pull the camshaft out, supporting it near the engine block.