1906117 Outer Valve Spring Fits Caterpillar Industrial Construction ModelOne New Aftermarket Replacement Outer Valve Spring Fits Caterpillar (Fits CAT) C9 and C9. 3 Engines This outer valve spring is a cylinder head component used in the Fits Caterpillar C9 and C9. 3 diesel engine valve train. The outer spring works in conjunction with the inner valve spring to maintain proper valve seating, control valve float at high RPM, and ensure consistent engine performance across the full operating range. This spring fits both