Hey guys, I need some help.
I recently replaced my timing cover (Holley 21-150) and my balancer (DORMAN 594012) on my 1985 305 TPI, but now it makes a constant hum that gets worse at higher rpm.

I took off all my belts and it continued meaning nothing to do with the accessories, I replaced the timing chain a month back and it didn't have this problem so it's most likely not that.

Any ideas and suggestions are appreciated!
Here is a video showing my problem:

 

Do you still have the old balancer? I think you might see where this is going.

 

One word: dorman

 

I watched the video and was left wondering how a balancer could make such a sound, unless it was slipping at the rubber joint? If it was slipping, the timing mark would now be in the wrong place. That sounds to me way more like something rubbing, could the new timing cover be being slightly contacted by the chain perhaps?

Anyway, I second Vader's idea, putting the old balancer back on would pretty much tell the tale of which is at fault here.....

 

I agree.


If you pause the vid at 0:03, at the point where the most light/least shadow is on the damper, it looks to ME like the damper outer ring has already slid back on the elastomer/hub.

 

Good eye Tom, it does look like the outer ring has slipped at the point you indicate in the video