How To Upgrade Your Valve Cover
If you have a '81 thru '86 258 with a plastic valve cover it leaks. AMC could not fix it and the only way you can is to replace with an aftermarket extruded aluminum one. Although a labor intensive upgrage it is fairly easy and should be the first thing you do for your AMC Eagle. You should plan to do this over a two or three day period, you will see why later.
An up front warning -- there was no rhyme or reason as to what holes AMC tapped for attaching replacement valve covers. Some have them all tapped while others varied. There are a couple of ways to tackle the untapped hole issue: 1) Tapping Holes or 2) Stud Alternative
The task at hand, getting rid of this:
There is a lot of stuff in the way of your valve cover and this is what makes it so labor intensive.
First disconnect your battery.
You will want to first mark both ends of every vacuum line you want to move out of the way. I used masking tape and numbered the ends.
One of your AC hoses may be in the way too. You may have to remove your compressor from the engine and move it out of the way with the hoses attached. This is a good time to replace your belts.
Also you need to disconnect the fuel line and remove any other item which will impede the removal and installation. You will thank your self for this as the job progresses.
Make sure everything attached to the old cover is also removed.
Also, remove the wiper motor completely -- this is easy, four bolts and a clip that secures the motor shaft to the wiper transmission.
Lastly, tie a rope around the wire loom (you may want to remove one or two of the loom retainers on the fire wall) and carefully pull it up and out of the way as far as you can. Secure the rope, I used the back bumper.
Now you should be able to actually remove the the valve cover. It is probably attached with a bolt in the back, one in the front and 3 on the passenger side. On the driver's side you will need to remove the larger nuts and retaining washers.
Even with all that you have done to provide working room getting the old one off will take some maneuvering -- tipping it towards the passenger side to clear the rocker bridges will probably work best.
Finally it is off -- reward yourself.
Thoroughly clean the mating surface on your head to prep it for the new cover.
First determine which holes are not tapped. Probably the ones on the driver's side then decide which way you want to tackle the untapped holes; see: 1) Tapping Holes or 2) Stud Alternative.
Once you have completed your attachment mods you are ready to proceed with putting the new valve cover on.
The instructions that came with your new cover will probably say to attach the gasket to the cover first. DON'T DO THIS! First, put your red gasket goop on the head and put the new gasket on it, lining everything up. Finger tighten the bolts to hold it in place and leave it alone for 24 hours.
Next day. Check your work - make sure the JB weld is fully cured. Remove the bolts that held the gasket in place. Place a bead of your gasket goop on the top of the gasket.
Carefully, and this will again take some finesse place the new valve cover in place. Snug down the nuts and bolts but do not over tighten. Just tighten to the point where it is good and snug.
Walk away for 24 hours for the goop to fully cure.
Next day. Resnug your fasteners. They will probably only need a little bit of retorquing.
Replace everything else make sure it all goes back as it was before -- hence all the prep work at first.
When you are sure you have it all done, reconnect your battery and fire her up. Check for leaks. If you took your time you will probably have none.
What I did was to purchase 4 short 1/4" diameter double ended studs as you will want to do this on the back one too and 4 of those round nuts (hex nuts will not clear) with the flat sides for a wrench to fit - better yet get the ones with the hex hole on top (really handy for the back one). Thoroughly degrease the holes, grind one end of the studs for the driver's side hole so they will fit snugly (you can screw the back one in) and then JB weld them in place (do not use the quick set JB weld)-- let these set up for a while until they don't wiggle.