I don't think being off a bit on the tightness of the plug is the main problem, I didn't put anything on my threads and didn't torque them either, (don't everyone squack at once). Here is why I think they pop out;

1: Many shops recommend using nothing on the treads and the torque values greatly differ if you do use something. Let's say 14 ft lbs; that's only 14 with nothing on the theads. The more slippery whatever you put on the treads is, the more you will be off on your reading. If you believe in the "high torque theory" you will be over torqued if not stripped out.

2: Dirt/grime/moisture in the plug hole can "lock up" a torque wrench and give you a good reading when it is actually zero.

3: Dirt in the hole can cause the new plug to wipe out the soft threads in the head. I recommend using brake parts cleaner in the spray can with the red tube on it, and then immediately blow out. I say immediately because is dries very fast.

4: Do your plugs one at a time so they get the attention they need. I think some people have a system where they put them all in finger tight and then go back and torque them all. It is easy to miss one with 10 cylinders so that one gets zero torque. He saved 10 minutes but paid a big price.

I do believe in using a torque wrench especially if you don't change plugs all the time. I just don't have one anymore. I think the main thing is to take your time and pay close attention to how the plug feels going in.

 

I see your points. However, if any of those were truly the baseline cause, then Ford would have never redesigned the heads to create more threads in the sparkplug holes. They would have just issued a TSB with solutions like yours.

 

I don't agree. Maybe I should have specified earier heads but these helpful hints pretain to later ones also. Sorry it wasn't helpful to you but we don't all keep up on the intricate details of every mechanical glitch. Ford re-did them because they realized they screwed up. Why would they keep issuing a bulletin as a band-aid and hope everyone reads it?

 

The only reason is the fact that the heads have literally only 4 threads....period.

 

It seems like all of the 2 valve modular engines had problems with spitting out plugs. Another fact that you guys missed is the fact that tapered seat plugs are used instead of washered plugs. I always use a torque wrench when installing plugs in any engine with aluminum heads. Just something about two different metals with different hardness and compatibility.

 

I didn't miss it if you read closely.

 

I have had extensive experience with spark plugs in aluminum heads, having been an aircraft mechanic for 25 years. Most of my work has been on older planes, and the earlier ones (back into the 1920's) used bronze inserts threaded and shrunk into the aluminum heads. By shrunk, I mean the outside threads of the insert are larger than the threads in the head - the head is heated to about 500 degrees which expands the inside threads of the head to where the insert can be screwed into it. Sometimes the insert will need to be chilled with dry ice before screwing it in. When everything cools down, the insert is virtually one piece with the head.

Sometime in the 1950's some manufacturers began using Helicoil inserts directly in the aluminum head. The aircraft spark plug Helicoils have a serrated "tail" that is swedged into the outermost end of the threads to lock the coil in place.

Airplane spark plugs are removed, cleaned, inspected, regapped, and reinstalled at least every 100 hours of operation. The threads in the heads have to be able to handle this repeated cycle of removal/replacement.

The bronze inserts sometimes seize to the spark plug threads due to lack of lubrication. The Helicoils almost never do. I believe that most of the problems of seizing are due to lack of lubrication or improper lubrication. Champion came out with a spark plug thread lube in the late 1960's that was found to work well on Helicoil systems, but seized in bronze inserts.

No aircraft piston engine has ever successfully used spark plugs screwed directly into an aluminum head.

If I had a automotive engine with aluminum heads but no spark plug inserts, I would Helicoil them at the first opportunity. The Helicoil offers two improvements. First, it results in strong stainless steel threads to hold the spark plug. Second, the outside of the Helicoil has a greater thread area contacting the head, which is able to withstand more abuse from cylinder pressures and heating/cooling cycles. The automotive designers figure that the spark plugs will be changed only once while in warranty, and so they rolled the dice that the aluminum threads would make it through that one remove/replace cycle, thereby saving $8-10.00 per engine.

 

I was referring more to the tapered seat design of spark plug that Ford uses as opposed to the washered design plug that the aftermarket and other manufacturers use more than the torque wrench. I didn't miss the torque wrench part. I just didn't see anything about the tapered seat design of the plug mentioned. I know for a fact that Ford has used the tapered seat spark plugs since the 50's when the car companies made their own spark plugs. It probably save a couple of cents per unit and Ford just never changed the design. It is not the best design to use in aluminum or other soft metal.

 

I posted this before on another plug blow out thread, but there is several issues here.
A: the threads are in aluminum and aren't very deep
B: the taper seat plug is very picky to the right torque, made more difficult by only a few aluminum threads
C: Alternate fuel users have found that the engines backfired and in some cases exploded the intake manifold on start up. Some who did extensive research discovered that ALL the spark plugs fire until the computer picks up the cam angle sensor, then the injectors are engaged and the engine starts. The problem is, that any fuel in the cylinder from a dirty injector that leaks while the engine is shut off, can cause a backfire on start up that can spit a plug. Failure, or even a dirty CAS, can cause misfires during operation that can have the same result. The misfire can also wreak havoc on the engine in the long term and cause premature rod bearing failure.
I have seen and used insert kits which I will probably use on all my plug holes should I blow a plug out. It involves a oversized drill and tap, locktite in a threaded sleeve, which then takes a standard type spark plug...

 

I have 2000 V-10 with 150,000 miles and have never had a plug problem.
Then again I dont let anybody touch my engine. I have only changed the plugs once and made sure to install them buy the book. I used antisize and torqued to specs!
Now many people take their trucks to a shop instead of the Ford dealer for this kind of work and alot of shops will have an inexperanced mechanic do a simple job like changing plugs. All you need is some one to over torque the plugs once.
Thats just my thery!
Years ago I worked at a shop and I seen somethings done, bad things!
Thats why I always check my front end after an wheel alingment. I recomend my alingment shop, but sometimes they leave lose bolts on the adjustment sleeves.

 

Last time I had ball joint put in they left the snap rings off them and 2 nuts of the knuckle which requires 4.

 

Bottom line is that it is just a poor design made worse by careless mistakes made during a plug change.

 

I had a body shop install a Warn Winch and bumper for me after an acceident.
The whole bumper tweaked the first time I used the winch!
The shop only installed four bolts to the frame when there should be eight!
Always check the workmanship!

 

I always do it myself unless I can't for some reason. They usually screw it up if I take it in.

 

Actually its a little different than some think. Inadequate thread count, aluminum heads, 100,000 mile recommended plug change intervals, thousands of heat cool cycles, all have alot to do with it. But , if you go to a ford dealer and talk frankly with the mechanics, larger ford dealers see up to 10 vehicles a week with the same plug issue. Having talked with several mechanics, they have seen first hand fords have had plugs spit out with as little as a few thousand miles on the vehicle. My friend had an 03 F250 spit 3 plugs out by the time the truck clocked only 30,000 miles and he bought it new. Bottom line is it was a poor design originally and the engines during testing didnt go through the heat cool cycles normal service engines are subjected to. Ford knew they had a problem, and the plugs spitting happened as late as on 05 2 valve crown vics, since I have an 05 cv and 1 spit out on me recently without warning.The issue with ford is ignoring that there is a problem. This is not an isolated issue, actually a very common issue.