2N8204 Gasket Fits Caterpillar 3406 3406B Truck Engines (2N-8204)One New Aftermarket Replacement Intake Manifold Gasket Fits Caterpillar (Fits CAT) 3406 and 3406B Truck Engines This aftermarket replacement intake manifold gasket seals the intake runners on Fits Caterpillar 3406 and 3406B heavy duty diesel truck engines, preventing unmetered air leaks and maintaining consistent combustion performance across all six cylinders. The Fits Caterpillar 3406 inline six diesel requires six of these gaskets one per intake