VetteNet How To: Replacing Smallblock Valve Stem Seals

Symptoms:

Recently I needed to replace the valve stem seals on my 1986 Corvette. The L98 engine had approximately 86K miles on the odometer. Some of the symptoms that lead me to performing the work appeared over the years. For some time I was experiencing a Service Engine Soon (SES) condition when cruising at 64-75mph. The SES light would come on and then go off. The error code was a code 45. The code 45 indicates a rich exhaust, and is triggered by the O2 sensor. I also noticed when changing the spark plugs that a couple of the plugs had black, oil deposits built up on them. The two plugs showing this were the ones closest to the firewall. This apparently is where the engine runs it hottest. Along with these symptoms, over the years, upon a cold start of the engine, there would be a noticeable cloud of blue smoke, that would clear once the car was running. Due to the smoke and rich exhaust, over time this condition would clog the main catalytic converter.

Tools Required:

Access to an air compressor.
Air compressor hose attachment that screws into the spark plug hole(s).
Torx bits.
Standard & metric sockets. >Valve spring compressor.
NOTE: Purchase the valve spring compressor type that fits over the spring and compresses the spring by turning a knob. DO NOT get the type that acts like a pry bar, as this one will not fit. There is not enough room to use the pry type on the L98 motor.
Valve seat oil deflectors (set of 16).
NOTE: These are optional, depending on if you need to adjust the valves with the motor running.

Parts Required:

Valve stem seal kit including seals for both Intake and Exhaust.
Replacement set of 2 valve cover gaskets.
Replacement set of 8 spark plugs (optional, but recommended).
EGR pipe clamp (obtain from GM dealer).

Approximate Costs:

Spark plug air compressor attachment: $6.00
Valve spring compressor: $20.00
Valve stem seal kit: $10.00
Valve seat oil deflectors (opt): $5.00
Spark plugs: Varies, $8.00 to $40.00
Rocker arm gasket kit: $8.00

Estimated Time to Perform the Work:

1 to 4 days. Figure on the car being out of service for several days.

Performing the Job:

Step 1:

Begin by removing the rocker arm covers. To remove the left side cover, you'll only need to loose the bolts holding the cover in place and gently work the cover off the head. To remove the right side, you need to remove the EGR piping. The EGR piping is the pipe wrapped in what looks like aluminum foil. It is connected below the distributor, with two torx bolts, and to a lower fitting by a circular clamp. Take care in removing the EGR pipe clamp, it may break. If it does, not to worry, an replacement can be obtained from your GM dealer for $2.67. I recommend replacing this clamp. Now remove the coolant intake hose to the plenum. Coolant will leak out, so be prepared to clean this up. Unscrew rocker arm cover nuts and gently remove the right cover.

Step 2:

Now that you have the rocker arm covers off, you can begin replacing the seals. Start by removing a spark plug from one side, leaving the others in, and screw in the air compressor attachment. WARNING: Do not tighten the attachment too much in the spark plug hole, because it's a pain to remove if you do!!! Supply air to the cylinder via the spark plug hole to hold the valve closed. Now remove the nut holding the rocker arm, doing both the intake and exhaust, and lift the rocker arm away. Note that the exhaust valve is the one that is lined up with the outlet to the exhaust manifold. The pushrods can remain in place. Position the valve spring compressor over the spring, and compress the spring enough to remove the retainer clips. There are two clips, and they are easily removed using a magnet once the spring is compressed. Remove the retainer and spring. Now you are ready to replace the two seals. There will be a small o-ring seal, and either a rubber "stopper" looking seal, or rubber cap seal, depending on which valve you are doing, the intake or exhaust.

Step 3:

Once the seals are replaced, you will replace the spring, still in the valve spring compressor, onto to the valve. Replace the valve spring retainers and clips. Once both intake and exhaust are done for that valve, you can release the air pressure from the cylinder and replace the spark plug with the new one. Replace the valve tappet and loosely tighten the bolt. Repeat these steps for each valve until completed.

Step 4:

Adjust the valves. Refer to a manual on adjusting the valves. There are two ways to do this. One w/the engine running the other not. If you decided to do w/the engine running, then you'll need the oil deflectors.

Step 5:

After the valves have been adjusted, replace the rocker arm covers with new gaskets, tighten down covers, but DO NOT OVERTIGHTEN. Replace all hoses removed. You're done! Start the engine and listen for a any loose valves. If you hear a ticking sound you'll need to pull the rocker arm covers again, and adjust the loose valves. You might also want to do a compression check to ensure none of the valves is too tight.

Lessons Learned and Good Suggestions:

Do not purchase the lever type of valve spring compressor, as it won't fit on a number of valves.
Do not overtighten the spark plug air compressor attachment in the spark plug hole, as it's difficult to remove.
Purchase a replacement EGR pipe clamp, maybe two, as the original one will probably break when removing. There is a special tool required for crimping the new clamp on the EGR pipe, but you can use a pair of dull side cut pliers and brute strength to crimp as an option.
The replacement of the EGR clamp was the most frustrating of the work done, as the seal must be good, or you'll hear an exhaust leak.
Use shop rags to cover the head openings (oil drainback holes), to protect from dropping dirt/tools/something into the engine, as this would be very bad.
Don't overtighten the rocker arm (valve) covers, as this can cause leaks.
You may need to use a socket over the valve stem when replacing the lower cap/boot seals, to tap it down to make a snug fit.
Two man job, nice to have another pair of hands around.
The o-ring valve stem seal goes on the SECOND grooved notch of the stem. Lower one if you want to look it that way. Take note as you remove the old seals. It's likely the old seals will be brittle, and will break apart when removing. Be sure to clean up the broken pieces.

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