They just get old and fail.

 

Sounds like an exhaust leak to me as well. But, you can take a 1" dowel or any good solid stick and put it against the engine in various locations with your hand over the receiving end and then push your ear against the back of yer hand. Makes a great homemade stethoscope. If it's a mechanical noise you pinpoint it that way. But I believe all you'll hear is normal noises. If you hear something that sounds like the Jolly Green Giant in yer engine with a 25lbs sledge, you found the problem.

 

I paid 350 for a new manifold gasket on just the passenger side with the cost of new studs and the removal of 3 broken ones.

SS studs would be a better replacement. But, like jethat said, for 350 you can get a set of LT headers that will yield you gains, sound and cost the same.

 

Reading this now and voting an exhaust leak, read here:

https://www.f150online.com/forums/v8...stions-10.html

And go forward a few pages, it has photos and shows you/explains what to do and how to do it. My manifold on my truck cost $180 I think shipped, studs cost $6 shipped for 10 of them.

 

I have a set of 5.4 stock exhaust manifolds off my 03 that were only on my truck for 10,000 miles. I can sell them for cheep and maybe we can meet up to save on shipping.
Let me know.

Phil

 

I keep listening to the vids, the first definitely sounds like an exhaust leak, the second vid... man, I dunno. Very consistent with rpm's. Exhaust leak will have a flapping sound from the gasket like in the first video and can be inconsistent. That second vid still sounds like a rod bearing to me. Would like to see a video of you reving it, a bearing should be more pronounced coming back from a high rev.

Here's a vid of mine. Listen and you can hear a few different sounds... an exhaust leak (the flapping), a rod bearing (mid to high rpm) and bad timing chain guides (ticking) That were all confirmed when the motor was pulled.



I can't find the video of it running steady at 2500-3000 rpms but it sounded very similar to yours. Im pretty sure there are 2 different sounds going on. could be wrong though.

 

Exhaust leaks can be missleading. I had the header bolts on my Mach I come loose once and I was sure I had a rod nock. tightened the bolts and it was all good..

 

You may be getting ready to launch a spark plug, the day before my 99 spit a plug I thought I had a bad lifter because I had a knock, next day - the #6 plug blew out of the head.

 

As a matter of fact, I just watched your 2nd video again, the one at idle. That is exactly how my truck sounded the day before it spit the plug out. What could be happening is one of your spark plugs may be on its last thread, and as the cylinder comes up on its compression stroke it pushes the plug up, then when after combustion the piston goes back down which sucks the plug back into its seat. Imagine that at 2k RPM's, the plug acts like a sledgehammer on those threads and it will blow out of the head. The best way to check is to run the truck at idle, and take a long extension and place one end on a coil, and the other end to your ear. If you have a loose plug, you will be able to hear compression (hissing) under the coil. I've been through this 3x and you can't heli-coil the plug back in after it blows out.

 

You can, but it won't last. The only inserts that will last are Time-Sert and the custom inserts used by the guys at blownoutsparkplug.com on their field service.

I'd pull ALL the cops and torque all 8 spark plugs back down to 28 ft/lb.