engine knock on startup
 

i have a 2007 expedition i bought new it has a 100K warrenty on it.
it stared to make a knock on startup that has gotten progressevly worse over time. the dealer installed new timing chanis and this did not help. it sounds like a rod or heavy detonation. it does not do it all he time. the dealer is blowing me off and saying he does not hear it. i have seen posts about cam phasers and piston slap and that if you complain enough they will replac the engine. need help

I had a tapping that just never went away at 10K miles, ended up replacing one of the heads. THen at 50K or so I got a marble sounding rattle on start up. It ended up being the timing chain tensioner gaskets and tensioner arms worn out. After they replaced that its fine.