I'm looking at a 2005 F150 with an 5.4.

Do the 05's have the same spark plug thread problem that the earlier ones had?

 

Yes. 04 --> 08... all the same.

 

Are the 4.6's less prone to this prob?

 

Yes. The 4.6 uses a 'traditional' plug design.

 

From what I understand, the 3-valve heads all have deeper threads that did the 2-valve heads and that fixes the issues with sparkplugs shooting out of the heads.

 

Yes. The problem is now one of retention, as the sleeve/shield is binding, below the seal and threads.

An interesting note - sparkplug blowout can still occur even on conventional plugs with full thread count heads, if intial overtightening, or subsequent and repeated R&R overtightening distorts the threads. Much less common, but not unknown.

 

What do you mean the problem is now one of retention?

 

The fact that due to deposit buildup between the bore and the ground shield/sleeve, the plugs are difficult to extract - some to the point of breakage.

You should try to look for the many threads that cover this in excruciating detail - or look at the vid linked in Stealth's sig.

 

LOL..Nice. Is that why everyone says you should use anti sieze? Ive read some threads where people suggested using anti-sieze and was curious as to why you would do that (especially when people complain about the plugs loosening up and shooting out of the heads).

 

On the 5.4 3V plugs, the hi-temp nickel anti-sieze is used on that shield mentioned above. In essence, to fill the void and presumably inhibit (or at least defer) the buildup of any more deposits and/or provide a coating that deters adhesion of same, and thus allowing extraction without the associated drama .

That vid explains it well.

Now, on conventional plugs a tiny bit of anti-sieze is preferred on the threads due to the dissimilar metals involved.

Strangely, NO thread anti-sieze application is recommended by Ford on the 3V plugs - and I have not, to date, heard a reason for this that makes any kind of sense to me. So, when I did mine, I followed an expert's advice - who's done many, many plugs, and applied a very small amount on the upper portion of the threads.