How to Install Valve Seals in a 350 Engine

by Dan Ferrell

Sonett72/Wikimedia Commons

The valve seals on your 350 engine might harden or break after years of service. A bad seal will lead to oil consumption and cause engine smoke at the tailpipe. You can service the engine and replace one or more valve seals yourself. However, before you begin, make sure you have all the tools necessary to perform the job and understand the procedure.

Top Dead Center

Step 1

Disconnect the black, negative battery cable using a wrench. Loosen the nut on the bolt holding the cable terminal to the post and lift the cable off the battery post.

Step 2

Set the transmission in "Park," if the vehicle is automatic, or "Neutral," if it is manual, and apply the parking brake.

Step 3

Follow the spark plug wire that connects to that cylinder toward the distributor cap and mark the distributor body with correction fluid just under the wire terminal.

Step 4

Disconnect the same spark plug wire from the spark plug. Grab the wire boot with your hand and twist it from side to side as you pull the wire off the spark plug.

Step 5

Remove the spark plug using a spark plug socket, ratchet and ratchet extension. Connect the ratchet extension to the spark plug socket and the ratchet. Insert the plug socket on the spark plug and unscrew the plug by rotating the ratchet counterclockwise.

Step 6

Remove the two mounting screws that secure the distributor cap to the distributor body using a Phillips screwdriver. Then lift the cap off the distributor with your hand.

Step 7

Rotate the crankshaft with a ratchet and socket attached to the crankshaft-pulley center bolt until the rotor points toward the mark you made on the distributor body. Now you have the cylinder with the valve you are servicing on top dead center, or TDC, position and the cylinder valves in the closed position. If your model is equipped with a fuel injection system, consult your car owner's or vehicle service manual to set this cylinder on TDC.

Remove the Valve Seal

Step 1

Remove the valve cover using a ratchet, ratchet extension and socket. Attach the socket and ratchet to the ratchet extension. Then position the socket on one of the valve cover mounting bolts and turn the ratchet counterclockwise to remove the bolt. Then proceed with the rest of the mounting bolts.

Step 2

Detach the rocker arm using a ratchet and socket from the valve you need to service. Attach the socket to the ratchet and position the socket over the rocker arm mounting nut and turn the ratchet counterclockwise. Then remove the rocker arm from the mounting stud.

Step 3

Insert a long piece of nylon rope into the cylinder through the spark plug hole using a screwdriver of the appropriate size until you have completely filled the combustion chamber with the rope. Make sure there is enough rope hanging out of the engine block so that you can pull it out after you finish installing the valve seal. The rope will prevent the valve from falling into the combustion chamber as you install the seal.

Step 4

Place shop rags around the valve you are servicing to prevent tools and engine parts from falling into the engine block.

Step 5

Compress the valve spring using a valve spring compressor.

Step 6

Remove the two small valve stem keepers using the pair of small needle-nose pliers.

Step 7

Release the spring compressor carefully and then remove the spring retainer, shield and valve spring.

Step 8

Slide the valve seal off the valve stem using the needle-nose pliers.

Install the Valve Seal

Step 1

Apply a light coat of new engine oil to the valve stem with your clean index finger and then install the valve seal on the valve stem with your hand.

Step 2

Install the valve spring, then the shield over the spring and finally the spring retainer.

Step 3

Compress the valve spring carefully using the valve spring compressor. Follow the compressor manufacturer's instructions.

Step 4

Apply a bit of assembly lube to the inside of the two valve stem keepers. The lube will hold the keepers in place as you release the valve spring.

Step 5

Position the two valve stem keepers in the valve stem mounting groove with your hand and then release the valve spring compressor.

Step 6

Remove the shop rags from the top of the engine.

Step 7

Pull the nylon rope out of the cylinder.

Step 8

Install the rocker arm on the mounting stud. Then start the mounting nut by hand and finally tighten it using the ratchet and socket.

Step 9

Service the next valve, if necessary, following the steps outlined above. Then position the valve cover in place and start the mounting bolts by hand. Using the ratchet, ratchet extension and socket, tighten the mounting bolt.