[Telfair]

I have a 98 Windsor 4.6L that was just rebuilt by a reputable company. When it was reinstalled in my truck there was a knock and somebody said it was loose tensioners allowing the timing chains to make a noise. They replaced the whole timing thing, chains, tensioners, etc.
After I got it backthey said put some miles on it, so I put 3000 miles on it. After the truck warms up I still hear a knock. I have had three other mechanics listen to it and I get a unanimous "piston slap", but these same mechanics say that the rebuilder will "make it right".
Does anyone have any ideas about where the knock would be coming from? It's not a sound like a rod, it's higher pitched than that.

 

[Mr Mac]

If it is piston slap it is typically caused by too much room between the piston sides and cylinder wall. If they somehow mismatched the pistons (easy to do in a shop) then it needs to be fixed soon before serious damage occurs.

Take it back to them as they seem willing to make it right. Make sure they drive it with you to hear it.