This document provides instructions for removing and installing inlet and exhaust valve springs on a Caterpillar C4.2 engine. It describes the required tools and gives step-by-step procedures for removing valve springs safely while ensuring the piston is at top dead center. Proper cleaning and inspection of parts is emphasized. The installation procedure describes compressing the springs, installing new seals, and ensuring correct valve depths are achieved. Safety notices warn of potential injury from compressed springs and ensure springs are replaced in pairs for each cylinder.