When installing a harmonic balancer, make sure the front key is in the crankshaft. When I had my engine out about 3 months ago, I guess the front key fell out of the slot in the crankshaft. Well, I installed the harmonic balancer anyways because I never noticed. Just last week I was driving down the freeway and I had a bad vibration coming from the engine. At first i thought it was a misfire, but when I got off the freeway and I got out of overdrive, I could feel how bad the vibration was. I limped the car home, and I noticed that the rubber on my harmonic balancer was coming out a bit, so I thought maybe the outer ring rotated out of position, causing the engine to be out of balance. I pulled the harmonic balancer out and realized that the keyway was ground up bad, due the the fact that the balancer had only been sitting on the back key, the one for the timing sprocket. Without the front key installed, I guess the force of the engine overpowers it.
So you guys can learn from my mistake, make sure the front keyway is in whenever you install a balancer! I'll try and get a pic of the damage to the balancer.

 

I couldn't see your balancer falling off to be a good thing!!! Good to hear that you were able to get it home alright.

 

ouch!

 

Now you've got me all worried about mine