I've read in these forums a shot of PB Blaster or other pentrating oil around suspect plug threads helps with the older style steel threads. I run a 5.4 gas V-8 and use nothing but the Motorcraft plugs along with a dab of nickel base anti-seize, torque slowly to 20 ft/lbs. With just over 254K miles not blown one yet!

 

I think you both are agreeing and my thoughts were the same too. During the 130K miles before I got it, the threads were damaged and the new plugs installed barely well enough to keep it going. Then when I removed the plugs to find a miss, that was the last "thread". Remember I said that they were not really tight the first time I removed them.

Anyway, here's a pix of the last two that blew out. If I wasn't looking for thread problems they would look normal.

PS. I'm saving my cop's with the broken flanges for emergency repair. They should still work, just need to fabricate a mount, right?

Thanks for your help, Great forum.

 

The plugs in the pic show a lot of corrosion on the threads due to the exhaust getting through, I believe. With the problems you have had you should get a repair kit from Sears for about $40.00 and carry it with you in the truck along with whatever tools you might need.
I have the kit I mentioned and used it on my Navigator with excellent results.

 

We must be seeing different pictures because there is no corrosion on the plugs in the pic he posted. There is some carbon on the first few threads but thats about it. The plugs look good.

 

They don't look like Motocraft or Autolite plugs to me, I went out and looked at one of the plugs I pulled out at 65K and there was no sign of carbon are anything else on the threads in fact they look like new. Someone really did a number on the threads before you got the truck.

Denny

 

I could be wrong, but don't those plugs look like the newer ones when Ford corrected the plug blowing issue? The ones from '99 had less threads, if I recalled correctly.

 

They look like the SP479 plugs which are the updated plugs that are speced for all the 99'-04' modulars.(Nickel plated) The Autolite equivalent is the AP103 which is exactly the same as the SP479 except the Autolite plug has a black finish. I never had issues with either plug. The extra thread length on the plug do not do anything if the head doesn't have the extra thread length also, obviously.

MC SP479
More Information for MOTORCRAFT SP479

Autolite AP103
More Information for AUTOLITE AP103

 

They are the SP479 plugs. I now have four inserts installed (2,5,7 &9). This is the scariest job I have ever done in my 50 years playing DIY mechanic, ie. eight hours procrastination--2 hours installation! Hope I don't need to drill any more holes in my heads, but I'll keep a few inserts on hand just in case.
I never would have done this without the help from this great forum. Thanks guys for your support and advice.

 

Good job! I had a plug blow out on me and had to do a "parking lot" repair. I definitely got a lot of weird looks in the process. The repair is still holding strong knock on wood.

I really need to check the torque on my plugs though. I haven't touched them in a few years