ok heres the deal a 99 f-150 with tow package 4.6 baby motor. was towing and lost all power run rough as hell heated up of course so dropped load let cool then it started up run rough headed home had no power on hills down hill could fly figured maybe coil pack gone get home and check all firing pull plugs 2 and 3 cylinder plugs burnt up porcelain gone even and 1 and 4 not much better did compression check couldnt build anything on 2 so i went to a leak down test air coming out intake bad valve right.. so i thought took head off none of the valves on the head close all the way my question is why? could the cam be worn into the journals that much only 155000 on truck or do i have bad lifters im totally stumped here how do i fix...

 

Any codes? Without actually looking at what you have it's difficult. There could be several reasons. If you started losing oil pressure or had low oil level the cams could have had oil starvation. This will cause the cams to to start seizing in the cam towers (bearings). When this happens there is so much resistance that the cam/cams start slowing down from the friction. Usually if it gets severe enough the timing chain will break. However even before that happens it can throw the cam timing out enough for the valves to make contact with the pistons. The loss of power could be from that problem or if the truck was overheating then the CHT sensor will signal the PCM to shut down four of your engines cyls. in fail safe mode. Overheating can also cause the plugs to break/burn from detonation caused by a lean condition. Inspect the piston domes and look for eyebrows where the valves hit the domes. Thats an indication that your valve timing went out. I would remove the cam caps and look for burning or melting of the aluminum bearing surfaces. Also look at the piston domes for any pieces missing around the top edges (upper land) This would indicate detonation. When the piston breaks the pieces bounce around on top of the dome and make contact with the sparkplug breaking the ceramic and bending the electrodes. The valves could also be stuck open because the face is bent or because the valve stem is bent and is stuck in the valve guide or because a valve seat is broken and a piece is missing or a piece of debris like ceramic is stuck and holding them open. Do the cams turn freely by hand? When you removed the timing chain was it tight or hanging a little loose? If you could post some pictures of the cyl heads that would help a lot. A fix would more than likely require a new or reman cyl head at least. At this point I'm really just kind of guessing what you have going on with this.

 

Sounds like you overheated it bad and may have lost lubrication. Read whay Dyno said, you need more infomration and especially some pics if possible. Melted porcelain and no ground tip on plugs means you got really hot. It probably had a lot of pinging to go along with it.