coyotedon

I have a 2012 F150 Supercrew with the 5.0. At about 40000 kms it developed an engine noise that is intermittent. It sounds like a really bad lifter noise. After several trips to the dealer they finally heard what I was talking about but told me that Ford says this noise is acceptable. I know if I was looking to buy a truck and heard that engine noise I wouldn't buy it but Ford says it's normal.Engine was built after the date of the service bulletin for timing tensioner.Any help would be appreciated.