There are several reasons why an owner would need to change the intake manifold gasket on a Mopar engine. Wear and tear tends to break down gaskets fairly quickly, especially for hot rod and racing applications. Also, any time a new intake manifold is installed, or any time that the existing intake manifold is removed for engine repair, a replacement set of gaskets should be installed as well. If you have basic mechanic skills and the right tools, replacing an intake manifold gasket is a relatively straightforward task you can complete in an afternoon.
Disconnect the battery. Drain the radiator and remove upper radiator hose. Unscrew the bolts for the thermostat housing and remove the housing. Pry out the thermostat with a flat head screwdriver and discard. Scrape off any gasket remnants.
Loosen the bolts on the distributor bracket. Use a grease pencil or chalk to mark both the distributor and the bracket with corresponding lines. This will make reinstallation easier. Remove the distributor.
Disconnect the fuel line, vacuum tubes and throttle linkage from the carburetor. Place a rubber plug in the end of the fuel line to prevent leakage. Carefully place the throttle linkage to one side, away from the intake manifold.
Remove the temperature gauge sensor from its port at the front of the intake manifold.
Unscrew all of the bolts around the perimeter of the intake manifold. Use a flat-head screwdriver or a putty knife to pry the intake manifold loose from the heads and the block.
Carefully remove the intake manifold. Some fuel may still be in the bowl of the carburetor, so be aware of possible leakage.
Scrape off any remnants of the old intake manifold gaskets on both the intake manifold and on the cylinder heads.
Use the silicon epoxy and apply a bead on the new intake manifold gaskets. Do one side at a time. Carefully apply the gaskets to the port plates of the intake manifold. Place the rubber liners at the front and rear lips of the engine block, and apply a bead of silicon to the top of each.
Apply a bead of silicon epoxy to the bottom side of the intake manifold gaskets. Line up the bolt holes in the manifold to the bolt holes in the heads and engine block, and carefully set the intake manifold in place. Bolt in the intake manifold.
Replace the thermostat with a new one, and reattach the thermostat housing. Reconnect the upper radiator hose. Fill the radiator with coolant.
Reattach the temperature gauge sensor, and reinstall the distributor. Line up the mark on the bracket with the mark on the rim of the distributor. Reattach throttle linkage, vacuum tubes and fuel lines. Reconnect the battery.
Start the engine and use the timing light to time the engine. Check the new intake manifold gaskets for any leaks of fuel, or bubbles that indicate an air leak.
