Why you should replace old harmonic balancers
 

When I first bought my C10 panel, I knew the outer ring on the balancer had moved, as I could never get the timing marks to line up. It has been a long term project so I finally got around to pulling the old balancer to replace it. Wow was I surprised how bad it was!!!

Folks, this is why you should never trust an old balancer. The rubber breaks down and then starts to fail. This is the worse one I have ever changed.

Ring not only spun but was walking out. The pulley kept it on.

http://gallery.lisaandmike.org/album...l/IMAG1266.jpg

From the backside, you can see the missing rubber and it pushing out. Glad I never drove this!

http://gallery.lisaandmike.org/album...l/IMAG1267.jpg

Re: Why you should replace old harmonic balancers
 

Good thing you caught that... It would've been an expensive mess under the hood coming apart at speed.

Re: Why you should replace old harmonic balancers
 

I recently bought a 1963 truck. When I spun the fan and fan belt by hand, the engine did not feel like it had good compression. I was told that the engine would run but I was not very convinced.
I cleaned things up under the hood and noticed that the harmonic balancer was spinning in place when I turned the fan belt by hand. I had another harmonic balancer handy and replaced it. Engine runs pretty good.