A while back I changed the original spark plugs out on my V-10 at 107,000 miles. This job has developed a bad rep over time that I don't think it really deserves, access, both up and into the engine bay (my EX is lifted 4" and rolling on 35"s, so kind of high) as well as to the rearmost plugs is the biggest challenge, not difficult, just less than comfortable. My son assisted with job and surprised me with how much he already knew as I explained each step, I guess he was listening all the other times he has helped me wrench! :-X04 I have seen where other owners have gone to much farther lengths to gain access by removing lots of other stuff to get at the plugs, I did not touch my fuel rails and only removed the air inlet tubing and one other smaller hose, I did move a couple of wiring bundles around as needed but didn't unplug anything other than the COP connectors. We spent about two hours doing this job including taking the pictures below and discussing each step.
Denso is the OEM manufacturer for Motorcraft COPs and boots, so for about half the price you get the same excellent quality parts from Denso, I ordered these from Rockauto.com.
COPs = Denso #673-6000 (didn't need a COP but ordered two just to have spares on hand in case of a failure on the road).
Boots and springs = Denso #671-0001
Plugs = Motorcraft SP-479 (AGSF22WM) pregapped to .054" but I rechecked each one before installation.
Permatex = Dielectric grease.
Attachment 284513

I had a can of very good never-Seez in the garage.
Bostic Never-Seez pure nickel special.
Attachment 284514

And I ordered the Gearwrench #80546 5/8" swivel plug socket from Amazon. This socket really was a big help dealing with the rear plugs as they are under the cowl.
From my local Ace Hardware store I bought 10 O rings to seal the boots into the plug wells. (helps to keep moisture or water from causing a miss).
Attachment 284515

The factory plugs all came out with no drama, there had not been any misses but they had all opened up a good amount from wear over 107K miles.
Attachment 284516
Attachment 284517

While the plugs were out I used a hand-held small bore camera to have a look into the cylinders, nothing of any concern was seen, just a bit of carbon here and there.
Attachment 284518
Attachment 284519
Attachment 284520

The new plugs were checked for the proper .054" gap.
Attachment 284521

Then treated to a light coat of the Never-seez on their threads and tapered seats.
Attachment 284522

The factory torque spec for the improved 7 thread heads is only 17 ft/lbs, seems pretty un-tight to me..... So I initially set them all to 30 ft/lbs and then finished them up to 32/34 ft/lbs. Adding the lubrication of the Never-Seez to the equation does require about a 20% increase to the spec to equal the specified "dry" torque. The older (mid-year '03 and back) engines with the 4 thread heads are only specced to have the plugs at 11 ft/lbs,but many DIY owners have seen excellent results at 24/26 ft/lbs.

EDIT: Correction to the above, Bostik recommends a 25% REDUCTION in torque values when using Never-Seez. However, the point of over torquing the plugs is well supported to counter the known plug ejection issue on these modular motors. Using a never-seez type product on any steel hardware being threaded into aluminum is a good idea to prevent galling and corrosion.
Attachment 284523

On the new boots you can see a recess that looks like it could hold an O ring, so I added one O ring to each boot.
Attachment 284524

The new boots with the O ring in place and a light coat of the dielectric grease. Both ends of the spring inside the boot were also given a dab of the dielectric grease to ward off any corrosion there.
Attachment 281576

These boots should be changed out at every plug change, they are cheap and they live in a very harsh environment where they do break down and develop small cracks that can bleed the high voltage passing through them and cause a miss.

To keep things easily serviceable I like to use the Never-Seez wherever I can, so the COP hold down bolts got a good coat of it.
Attachment 284525

With the new plugs, springs and boots I did notice quicker starts and slightly better throttle response and pickup. The following week we towed the 11,300 lb TT up to Niagara Falls and back, that return trip netted the best towing MPG that I've seen yet at 9.5 MPG thanks in part to these new plugs I'm sure. :-X06

Very good. Yes I have never had an issue. I use a 1/4” air ratchet to remove the 7mm coil bolts and a 3/8” air ratchet for the plugs. Takes me all of 20 minutes or so. Now the plugs on a 5.4 F150 of the same years is a PITA, and the 3 valve made that job worse. But on the SD and X’s it is easy. I did mine at 50k and again at 100k. I don’t like to wait till the 100k Mark, as the coils are working harder when the gap gets larger!

Tom, could you fix the link in the tech folder? (V10)b, I think it’s missing a ‘]/url]’ . :-X22

Lol, no Sean I can't, my moderator super powers only work in the towing forums, not here at the EX home base. That old naked bacon fryer will have to fix the link. ;). I dropped him a note about it, thank you. :)

You are correct, I was thinking backwards again there, thank you! Bostik recommends decreasing torque values by 25% when using Never-seez, I will edit the above to show that.

That looks like a good idea.
What size O-rings did you use?

I think it’s time to outsource, I’ll have my Admin contact your Admin and we’ll meet at Delaveaga to sort out. :-X06

Third pic from the top shows the card at the hardware store, 13/16" I.D., 15/16" O.D. 1/16" thick. They fit perfectly on my Denso boots, like they were made for each other. :-X22

Thanks Sergy! :-wink
Yes, Niagara Falls is a great place to visit, we have visited there several times, there is always something new to see up there and it's an easy walk to a foreign country!