360 Valve Stem Seal Replacement

Contributed By: Jeff Wynn

**This information is provided with no warranty, expressed or implied. It worked for me, YMMV.**

My least favorite part of my 73 J-4000 was the fact that every time I cranked it up, it belched ugly blue smoke, much to the chagrin of my environmentalist friends (and myself).

This writeup should help you change out those nasty, cracked, broken and melted valve seals that give you that characteristic "poof" of oil when you crank up your FSJ after letting it sit for a few hours. For whatever reason, AMC V-8's seem especially prone to valve seal wear.

Head removal is *not* required unless you drop a valve into the combustion chamber. The procedure really isn't all that hard if you have the proper tools and some experience working under the hood.

While the general procedure outlined herein may be applicable to many other motors, this writeup is specific to the AMC 360 V-8. Check your service manual for details about other motors.

Time required: 3-5 hours.

Special Tools/Parts:

1. Air compressor.
2. Chuck for compressing a cylinder through the spark plug hole.
3. Valve spring compressor (prise bar type). Chevy compressors work.
4. A set of valve cover gaskets
5. Appropriate RTV for valve cover gasket.
6. 16 valve seals (2 packs). The ones I got from Motion auto parts were nylon, and very similar to the originals. Napa offered some rubber ones that looked kinda flimsy, so I avoided those.

The Procedure:

1. Take some time to remove the air filter housing, fuel filter, miscellaneous parts, vacuum lines, and hoses that might get in the way of working around the valves.
2. Remove the valve covers, keeping close track of those little bolts and retainers that are on some 360s. At this point the rockers, pushrods and valve spring assemblies will be visible. Take a moment to ensure that the drain holes are clear of debris. My drains had a substantial amount of gasket and valve seal material. At this point, you can choose to replace the seals one cylinder at at time, or the entire batch at once. Unlike some motors, AMC's 360 has each rocker arm attached to a stud, allowing you to proceed one cylinder at a time. Regardless, remember which parts came from which valve as it is *critical* to put the pushrods, rocker arms, and the whole bunch of stuff back in *exactly* the same position as when you took it out. Keep in mind that the springs, retainers and keepers are different on the exhaust and intake sides. I chose to do one cylinder at a time, so here's what I did:
3. Remove rocker arms and pushrods from one cylinder, remembering which one is which. (Aside: now is a great time to check those pushrods for bends by rolling them on a flat surface.)
4. Remove spark plug and fill cylinder with compressed air. You'll hear air escaping from your cylinder, so make sure your compressor is on. Use 75 psi or so.
5. Gently rap on the exposed valve stem and around the keepers with a hammer and punch. This will loosen up the keepers so when you actually compress the spring they can be easily removed. Without this "persuading", you may not be able to separate the keepers from the valve stem. ** at this stage, it is helpful, but not necessary to have an assistant**
6. Bolt the spring compressor on the stud over the first valve. Important: make sure to use your ratchet to get a few turns on the stud, as just "hand-tight" may not thread the nut enough to keep it on the stud when you compress the spring. If the nut lets go, you may tear up your threads and have to replace the stud.
7. Compress the spring, while grabbing (or having your assistant grab) the keepers. The more you compress, the easier it is to grab them. The keepers are *very* small and prone to easy loss. Make sure to keep track of them.
8. Unbolt the compressor, remove the spring, retainer, and old seal.
9. Do steps 6 and 7 for the other valve.
10. If you have nylon seals, you'll need to soak them in hot water and gently tap them on with the provided tool. Otherwise install as the instructions say. You should have both valve seals for a particular cylinder replaced at this point.
11. Place assembled spring and keeper back on the valve steps and bolt the compressor back on the stud. Don't forget to ratched that nut down a coupla turns!
12. Compress the spring and replace (or have your assistant replace) the keepers. Again, the more you compress, the easier it is to put those buggers on right. Repeat procedure for the other valve. At this point, you don't need the pressure to hold the valve stems, so decompress the cylinder and replace the spark plug. **Important. Make sure not to accidentally depress the valve with the compressor as the cylinder may decompress. if this happens, you may lose the valve down into the combustion chamber.**
13. Replace the pushrods (*in order*), jiggling them a little to get them all the way down. Torque down the rocker arms to 23 ft-lbs.
14. At this point, just repeat the procedure for each of the cylinders.
15. Clean up your valve covers and areas where the gasket seals on the head, and put the valve covers back on.
16. Attach all those vacuum hoses, and other stuff that got in the way of the spring compressor.
17. (Optional) disconnect the spark and crank the engine a few times to get the oil flowing up the pushrods.

That's it!! You can now crank up your pride and joy without embarrassment.

Jeff Wynn, ATC Computer Nerd
Tue, 18 Mar 1997

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