Replacing valve stem oil seals on AMC V8 with nylon rope method. 

A sort of how-to guide with video clips of me replacing the valve stem oil seals on an AMC V8.
The valve stem oil seals are little mushroom shaped plastic or rubber caps which sit around the top of the valve stems inside the valve springs, to prevent stray oil splashes running down the stems and into the intake and/or exhaust manifolds. You'll know if they are broken and need replacing if you get a cloud of blue-white oily smoke out of the exhausts at startup after the engine has been sitting for a while, but it clears once warmed up and otherwise runs normally.
There are two ways to do this without removing the cylinder heads - either you make a fitting and put compressed air in the cylinder to keep the valve up against its seat while you remove the spring, or you stuff something inside the cylinder and move the piston up to physically jam it in place. Quarter inch nylon rope is ideal for the latter, and I had some, so that's what I used. About a four foot length is enough, and can be reused for each cylinder. You'll also need a valve spring compressor which can be used while the cylinder is in place (some are not suitable - check before you buy!). I made a simple lever one from steel offcuts welded together, which fits over the rocker stud to press down on the valve retainer, with a suitably large hole in the middle to get the retainer clips out & back in again through.
Rather than drone on and bore you while I was doing this, I tried to keep quiet (apart from an odd thud when my head hits the hood - and I think I did well not to swear!) and have typed up a few instruction pages in between the clips & photos. I think I've covered just about everything, but forgot to mention it's a good idea to stuff rags into the oil return holes at each end of the cylinder heads while you're working on the valves, in case the retainer clips spring off and drop down there. Just make sure to remove them when finished!
I know there are other how-to guides on here, but I think this might be the first with an AMC? It's a 390 in a 69 Javelin SST with about 70,000 miles on the clock, and several of the seals had broken completely, as you can see in the photo at the end. After this little upgrade with a new set, the cloud of smoke startup has disappeared and it smells less oily while running too. Hope you find this useful!