2418386 Inner Valve Spring Fits Caterpillar Industrial Construction ModelOne New Aftermarket Replacement Inner Valve Spring Fits Caterpillar (Fits CAT) C9 and C9. 3 Engines This aftermarket replacement inner valve spring fits the cylinder head valve train assembly on Fits Caterpillar (Fits CAT) C9 and C9. 3 diesel engines. The inner spring works in conjunction with the outer valve spring to keep intake and exhaust valves seated against their seats during engine operation, and is typically replaced during cylinder head