If the engine has been removed from the car, disregard the following steps which do not apply. For the left-hand manifold with 403 cu in or 455 cu in engine, disconnect the battery, remove the air cleaner assembly and disconnect the hot-air pipe to the manifold, and remove the hot-air shroud around the manifold. Raise the car and support it firmly on jack stands, bend back the metal retainers around each manifold bolt head, then remove each of the bolts, and disconnect the exhaust pipe from the manifold, using penetrating oil if the fasteners are 'frozen' in place. Remove the flywheel lower cover and the starter brace, wiring, and starter, then remove the exhaust manifold from under the car. For the right-hand manifold with 403 cu in or 455 cu in engine, disconnect the negative battery cable, hoist the car, and support it firmly with jack stands. Remove the right front wheel for better access, disconnect the exhaust pipe where it connects to the manifold using penetrating oil if necessary, and remove the exhaust manifold bolts before taking the manifold out from under the car. For the left-hand manifold with 260, 305, or 350 cu in engine, disconnect the negative battery cable, remove the air cleaner assembly, hot-air pipe, and hot-air shroud, then remove the generator or air conditioning brackets where they attach to the exhaust manifold. Disconnect the exhaust pipe where it connects to the exhaust manifold flange, using penetrating oil if needed, pry back the metal retainers from the bolt heads, and remove each of the bolts securing the exhaust manifold before removing it from above, noting that on some late models it may be necessary to disconnect the intermediate shaft of the steering column for better access. For the right-hand manifold with 260, 305, or 350 cu in engine, disconnect the negative battery cable, hoist the car, and place it firmly on jack stands. Disconnect the exhaust pipe where it connects to the manifold, using penetrating oil if necessary, remove the right-front wheel for better access, pry back the metal retainers from the bolt heads, and then remove each of the manifold bolts before taking the manifold out from under the vehicle. For installation on all models, the process is the reverse of removal, ensuring that new gaskets are used at the manifold-to-engine block and at each of the disconnected exhaust flanges, tightening all fasteners to proper torque specifications, adjusting all belts to the proper tension, and upon completion, running the engine to check for exhaust leaks, using a soapy-water solution brushed onto suspect areas to help find any leaks.
Posted by GMPartsGiant Specialist 
