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TOOLS
- Ratchet (preferably a torque wrench as well, but not necessary if you use come common sense when dealing with aluminum heads)
- A SPARK PLUG SOCKET, not a regular deep-well socket. There isn't anything protecting the insulator in them. A plug socket should also 'grab' the plug instead of letting it drop onto the ground/somewhere in the recesses of the vehicle. A regular socket can work in a pinch, but being careful is an understatement. I only ever see two commonly used plug sockets, and both the 3100 and 3.1 use the smaller of the two. I can't remember the size off-hand.
- Different sized extensions for said ratchet (each platform likely has a "best combination" for the rear bank of FWD cars).
- For checking the plugs, I recommend a small, soft brass brush to clean up the electrode and ground strap if you plan on reusing them. If you're changing regardless, this is unnecessary.
- Plug gapper/gauge
- Some silver or copper based anti-seize compound (dielectric grease can also be used, but isn't quite as good as the anti-seize).
- Dielectric grease for the plug boots
- Depending on the platform, a 13 and 15mm ratchet/socket/wrench. That combo will work for a W with dog bones up on top of the core support. Others may need a different combo or something entirely different for the different mounting schemes.
PROCEDURE
OK, we should be good to get started now. Pulling the front plugs is about as easy as it can get, just pull the boot off of the plug (TWIST as you pull to help prevent the terminal from ripping off of the wire), stick on your socket and whatever extensions you might need and turn counterclockwise. It would be best if the engine hasn't been run for some time since there is a possibility of damaging the threads on a hot motor when you pull the plugs. It seems to be more relevant to aluminum heads than iron, but I would apply the principal to both honestly.
Got the front three out? OK, now (if you have a W-body with a 2.8, 3.1 or 3100 (and probably more)) grab your 15 and 13mm tools. See where the dog-bones mount on the motor? Take them off. When that's done, go get in the car, set the parking brake and put the transmission in neutral. Get back out and see how incredibly easy it is top rock the motor back and forth? Well, for the rear plugs it makes it MUCH easier to mess around with if you have the motor tipped forward. To do this, stick one of the dog-bone's bolts through the mount and pull the motor forward with one arm and slip the bolt and dog-bone behind the mount (3100) so it holds it forward or use the little otherwise pointless bracket on the coolant hose to hold it forward (yes that's what it's for). A ratchet strap or rope could also be used (and admittedly is a bit safer and may give more working room) but isn't necessary.
Now that the motor is rocked forward, pull the boots off of the rear three plugs, again twisting to not disconnect the terminal from the wire. Pull the plugs and let's take a look. If you're running on a custom tune, the link shown below is a GREAT reference made by Bruce Plecan (Grumpy of TGO). Even if you're not running on anything other than the stock tune, it's a good reference as to how your motor is doing. Now the catch here is that you have to shut the motor down in the same situation that you want to see how the motor is doing, meaning you can't tell if your WOT mixture is right if you shut the engine down at idle...
Now would also be a good time to see how the gap has changed since they were installed. If there is obvious mechanical damage (no gap at all due to the ground strap being pushed into the electrode), you should have noticed a VERY abrupt change in the way that your motor operates and should keep a VERY close eye on possible reasons why (rod stretch at high RPM, incorrect plugs, damaged heads, etc). Also keep track of which plugs came from which cylinders to reference for future insight.
If they all look decent and don't have that many miles on them, you can clean them up and re-install them. Take that little brass brush and go over everything until all deposits are gone and it doesn't make any difference to continue brushing. If you can't get rid of some deposits, brake cleaner or carb cleaner should help dissolve them. After cleaning or if you're using new plugs, check the gap. The little gap opening portion of it should be self-explanatory as well. If there is too much gap, tap the ground strap lightly against some wood, that will close it up without causing any damage.
OK, now that the gap is set and the plugs are clean, grab that anti-seize and put a SMALL amount on the last 3-4 threads furthest away from the electrode. This will serve for a few purposes: silver and copper are GREAT at transferring both heat and electricity and also will allow you to remove them easier in the future due to a slight lubricative property and them helping to seal out any moisture that could get in between the plug and head and start corroding metal. Now, you don't want to coat all of the threads due to the threads potentially sticking into the chamber and then the compound getting baked into place. I don't know if there is the potential for damage, but it's something that shouldn't be there.
Now, lets start with the rear plugs since the motor should still be rocked forward. It's easiest to stick them in the plug socket (since it should grip the plug) along with an extension or two and start attempting to thread them in the areas where they came out. It will probably take a few minutes of fumbling around to finally get them to the exact perfect angle to start threading without a cross-thread, so try not to get any dirt/rust on the plugs. When you have them started, keep tightening until the resistance felt is obviously the plug seating, not a burr in the threads. At that point, a torque wrench would be great (if it would fit). For a 1995 3100, the first ever plug installation in a new head is spec'd for 20 lb-ft, and every time after is 11 lb-ft. That's not a whole lot of torque. If you're not using a torque wrench, just get them tight, then another 10-15º of torque should get you pretty close.
Now that the rear plugs are in, grab the plug boots of the rear 3 cylinders, and grab a small flathead screwdriver and dielectric grease. Put a little glob of grease about 1/2 to 1/3 the size of a pea on the blade of the screwdriver and smear it around the absolute edge of the inside of the boot. This will make removing the boots SO much easier than if you don't and it will also help prevent any kind of "spark leak" near the plug since dielectric grease blocks electricity. Now you can put the boot on the plug and twist it a bit to make sure it contacts everything. Repeat another two times and the rear is done. You can clean off the terminals on the coils using the brass brush if you want and basically do the same process, but on a 3.1 and early LQ1s, that's a pain compared to the 3x00s.
Time to rock the motor back to where it should be (or even further if you REALLY need the room). The front 3 are basically identical to the rear 3, so just repeat those steps.
Now that all the plugs are in and wires are connected, get the dog bones in place and torque them to 35 ft-lb of torque. You should now be done. Start the vehicle and see if there is anything wrong visually and audibly. If nothing, go for a little test drive and see if there is any odd power loss. If you somehow picked up power, you waited too long to change/clean your plugs and/or plug wires or just had the wrong plugs from the start.