The valve cover has studs and not bolts, very big difference.
I believe the valve cover nuts should be torqued to 8 ft*lbs, which is usually a little more than hand tight. I once used a 3/8" drive click type torque wrench to get the torque to the spec and I couldn't feel the click.
Studs are essentially 2 bolts without a head joined at the top, a crude representation is like <//////===//////>. The studs cannot be hammered out because they are threaded into a closed end hole in the head. Pounding on one will only cause further damage.
As for fixing the stripped studs and nuts (this is gonna be long):
First remove the valve cover.
Any studs that are stripped on their exposed thread need to be unscrewed. Simply use pliers or vice grips to grab onto the exposed section and unscrew them. Inspect the lower (hidden) threads for any damage, likely indicated by bands of aluminum stuck between your threads, I will explain later how to fix.
Any nuts that are stripped need to be replaced. Any that were used on the studs that have the upper sections stripped should be replaced to prevent further damage.
Some studs have a small hex on the center shaft for a wrench to be used in screwing/unscrewing. If no hex is present, carefully grip the center only to tighten them. The diameter of the center of most studs is larger than the diameter of the threaded areas.
Now, for the "forever spinning nut":
The hole in the cylinder head for the stud to thread into is most likely stripped. I'm guessing the center of the stud is too large to fit through the hole in the valve cover, and thus why it can't be pulled out.
Once the valve cover is taken off, I'm assuming that stud and nut will come off with it. The valve cover might be a little difficult to remove as a result. Once it is off either grip the stud with pliers and undo the nut or simply cut the stud to get it out of the valve cover..
Now you have to deal with the problem of a stripped hole in your cylinder head, which is where things get tricky and expensive. Be very careful as one error could cause the entire cylinder head to become worthless.
If you found any studs that show signs of thread damage as I mentioned above, start up here to fix it the correct way.
First off, you will need to know the specs of the stud. Specifically the length of the hidden threads, thread diameter, and thread pitch; diameter and pitch are given by in this format M3, M3.5, M4, whatever.
Now you need a thread repair kit. Depending on the specs and type of kit, these can range from $20-$80+ for one kit. During my summer internship I used the
Helicoil system to rework holes in aluminum arms used on the Corvette's convertible top. Helicoils are used by many manufacturers for threaded holes in aluminum, such as threads for studs in engine blocks.
You will need a kit (matching the wanted thread pitch and diameter) with a drill bit, thread tap, repair coils, and the insertion tool. The repair coils will likely come in different lengths so pick one that is close to the correct length.
This will be much easier if you remove the head before beginning these next steps. The problem stud is already removed from the cylinder head.
First step is to completely seal the exposed cylinder head to keep any debris from entering the cylinder head. Use tape and plastic, similar to painting prep.
Next, use the drill bit and preferably a drill press to drill out the stripped hole. If you don't have access to a drill press just use a hand drill and make sure it goes straight in. It is crucial that the hole you drill is centered over the existing hole and the hole is drilled straight, messing up either of these will ruin the cylinder head. Make sure to clean the hole so no debris is remaining inside it.
Now use the thread tap to tap the hole. If the threads cannot be made entirely then you will have to make the hole deeper, possibly even to the point of a through hole. Once again, clean all debris from the hole.
Now put the repair coil onto the insertion tool and begin threading it into the new hole. Using a coil that is the exact depth is ideal, then a longer coil, but try not to use a shorter coil. Thread the coil in as far as it will go. If you made a through hole thread until the notch by the tang is flush with the surface.
Remove the insertion tool and use a small punch to remove the tang by gently tapping it with something small. A hammer is usually too large and can risk bending the coil leaving it unusable and difficult to remove. Trim the top surface to make sure the coil does not extend past flush with the surface of the head.
Repeat this for each damaged hole.
If you want to half-ass this you can try re-tapping the holes without doing any repair to them and see if the threads will hold. I strongly suggest not doing this, the threads will be much weaker and will be very easy to strip again.
Another solution is to take the car to a machine shop and pay them to do the work for you.
Sorry for the humongous post but that is how you properly fix your problem.
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