The document provides instructions for removing and installing a camshaft on a Caterpillar 3126 engine. It describes removing components like the governor, side covers, and front cover. It instructs turning the crankshaft to top center compression for the number 1 piston and installing a timing bolt in the flywheel for installation timing. Removal involves removing retaining bolts and carefully extracting the camshaft. Installation is the reverse process. Guidelines are provided for determining if parts can be reused.