GM 12578511
Camshaft

You can start the exhaust camshaft and lifter replacement by removing the camshaft cover along with the upper Timing Chain Guide. After installing the sprocket holding tool (J 43655) you must remove both intake and exhaust camshaft sprocket bolts while discarding them. Mark the camshaft caps as they are separated so you can easily return them to their initial positions before moving them forward. Cautiously loosen each bolt on each cap for a single turn before ending the spring tension on the camshaft and ultimately removing all caps together with the exhaust camshaft and roller followers and hydraulic adjusters. Before fitting the parts, apply lubricant to the valve tips and place the hydraulic lash adjusters and camshaft roller followers following the same alignment as the camshaft sprocket. Add the exhaust camshaft together with camshaft caps while employing a three-turn installation order to a final torque of 10 n.m (89 lb in). The installation continues with camshaft sprocket attachment to each camshaft while finishing with new bolts that receive hand tightening only. Implement the sprocket holding tool (J 43655) to eye up the camshaft sprocket bolts until they reach 85 n.m (63 lb ft) with an additional 30-degree angle. To complete installation place the upper Timing Chain Guide then tighten it to 10 n.m (89 lb in) while putting back the camshaft cover.

The first task for exhaust camshaft and lifter replacement involves taking out the camshaft cover and upper Timing Chain Guide. You must install sprocket holding tool (J 43655) while you remove both intake and exhaust camshaft sprocket bolts which will be discarded. Note down the original positions of bearing caps before sliding the camshaft sprockets forward. The transmission of camshaft spring tension should stop by loosening each bearing cap bolt one rotation at a time before removing all caps along with the exhaust camshaft and camshaft roller followers and hydraulic element lash adjusters. The valve tips require lubrication during installation followed by placement of the hydraulic element lash adjusters and camshaft roller followers while verifying alignment notches on the camshaft sprocket. The exhaust camshaft and bearing caps should be installed before torquing the bearing cap bolts with incremental three-turn rotations until full seat is achieved at 10 n.m (89 lb in). Following placement of camshaft sprockets to camshafts use hands to tighten new sprocket bolts until you remove the sprocket holding tool (J 43655). Press the camshaft sprocket bolts to 85 n.m (63 lb ft) while adding another 30 degrees and complete the procedure by installing the upper Timing Chain Guide with 10 n.m (89 lb in) torque before finally installing the camshaft cover.

Ensure that used roller followers are returned to their original positions on the camshaft; if replacing the camshaft, also replace the roller followers actuated by it.

Mark the camshaft bearing caps for proper reinstallation, then remove the bearing cap bolts and caps.

Carefully remove each bolt on the bearing caps one turn at a time to relieve spring tension on the camshaft, then mark the bearing caps for proper reinstallation.

Ensure that used roller followers are returned to their original positions on the camshaft; if replacing the camshaft, replace the roller followers actuated by it as well.

Install the camshaft sprockets onto the camshafts, hand tighten new camshaft sprocket bolts, and then remove the Sprocket Holding Tool (J 43655).