91 GM Harmonic Balancer

[Mightiestmike]

At Idle after car is warm. I get this ridiculous loud knock low down in the motor. I've had one person tell me its a main bearing and another tell me its just the harmonic balancer. Has anyone had this problem with the Ford 5.0 L 302 CID ???

[fredjacksonsan]

The noise only occurs at idle, and if you rev it, it goes away?

Have you opened the hood and listened, to try to locate the source of the knock? If it's a bearing then you're probably looking at a rebuild. If it's something outside, you should replace whatever is making the noise.

A little more description would be helpful.