5F3112 Outer Valve Spring Fits Caterpillar Engines D315One New Aftermarket Replacement Outer Valve Spring Fits Caterpillar (Fits CAT) D315 and D318 Engines This aftermarket outer valve spring is a direct replacement for the valvetrain assembly in Fits Caterpillar D315 and D318 diesel engines. Valve springs work in tandem with the camshaft to ensure precise valve closure after each combustion cycle the outer spring works alongside the inner spring (5F3111) as a dual spring setup to maintain proper valve