Knock on idle

[SwedishMark]

Hello!
Just bought (today) a spare parts Mark Viii and then it started knocking on idle. It's not inside the engine but somewhere around it. Perhaps a pulley or something.
Anyways, it knocks on idle but if I rev it up there's nothing. Smooth as a pancake.
Anyone got any ideas exept for my theory about a loose pulley?

 

[87TTOPGT420]

Pull belt off start spinning

Ac clutch could be the knock or water pump other noises are usually bearing related idler pulley or belt tensioner pulley

Quick Check to verify its not engine is pull belt and start up and run briefly less then a minute

 

[SwedishMark]

Cheers for the help!
Yeah, I'll pull the belt off and start it up to see. How is the tensioner? I'm used to the tensioner on the 5.0s in the Fox-bodys. Is it pretty much the same?

 

[Stangman]

I think Laser had a problem simillar to this, turned out to be something to do with the timing set?

 

[SwedishMark]

I can give you guys a feedback on what was wrong.
It's the AC that makes the noise. The whole pulley is all loose on it and I have no idea how to fix that at the moment. But the car works anyways and we'll see when something drastic happens.
I got a spare AC too from the guy I bought the car from and guess what. All rusted and siezed together How generous!