Chevrolet 12637647 Exhaust Manifold

Disconnect the cable from the negative terminal of the battery. Raise the vehicle and support it securely on jackstands. Working under the vehicle, apply penetrating oil to the exhaust pipe-to-manifold studs and nuts, which are usually rusty. Remove the nuts retaining the exhaust pipe(s) to the manifold(s). Disconnect the spark plug wires, remove them from their retainers and lay them out of the way. Remove the exhaust manifold fasteners. Remove the manifolds along with the heat shields and discard the gaskets. The heat shields can be removed at this time. Check the manifold for cracks and ensure the bolt threads are clean and undamaged. The manifold and cylinder head mating surfaces must be clean before the manifolds are reinstalled-use a gasket scraper to remove all carbon deposits. Position the manifold on a bench and install the heat shields, bolts, and gaskets onto the manifold. Retaining tabs surrounding the gasket bolt holes will hold the assembly together as the manifold is installed. Place the manifold on the cylinder head and install the mounting bolts finger-tight. When tightening the mounting bolts, work from the center to the ends, and use a torque wrench. Tighten the bolts in two steps to the torque specifications. If equipped, bend the locking tabs back against the bolt heads. The remainder of installation is the reverse of removal. Start the engine and check for exhaust leaks.