I had a noise start abruptly on my 98 f150 with a 5.4 coming from the front right head region. A friend of mine said it was probably a timing chain issue. He was right. The right side guide had dissinagrated. I replaced that in hopes that it would cure the problem but when I put it all back together there is still a noise coming from the head area. I'll try attaching a video below. I've owned this truck since it had 30k miles on it (currently sitting at just over 220k) so I know it's history well and I have had no serious issues with it up until now. I. Hoping someone can help diagnose the problem or at least give me a good starting point. The higher piched noise in the video is just the belt sqealing. Thanks in advance.

 

Here is another video with the belt off so you can hear the noise clearly

 

Based on the fact the the noise had started after the timing chain guide fell apart-
I suspect you might have bent a valve when your timing chain guide disintegrated. Depending on how bad the guide was, it can cause the cam to be out of timing by a few degrees causing piston - valve interference

How did the front end of the motor look when you had the timing cover off? was there much sludge? Another less likely possibility (given the mentioned circumstances) is you might have a gummed up lifter.

Couple ideas to throw out there:

1. Try a compression test on the cylinder where the noise is coming from to determine if the cylinders hold pressure or not. If not, likely bent valve.

2. Pull valve cover, check for collapsed lifters. Rotate engine by hand and watch position of valves when valves are seated and make sure both valves come up all the way.

Hope this helps man,

Good luck!