New HBalancer is coming off! What did I do wrong?

[Isaiah92260]

I installed a new H Balancer and water pump last weekend, so for be past 2 week my fan slightly hits the new double V Belt HBalancer when idling... Today it started hitting it really hard and when I opened the hood, "Holy Cow"! You can tell the H Balancer has been slidding off :/. It came off about a half inch or more.... What did I do wrong? I made sure I installed the woodruff key, and the crank snout did not look work out at all... I'm not gonna tap the crank and add a bolt, I don't have the tools and don't want to damage anything, I have to call out of my second job today so I can get the radiator off and hammer the HBalancer back on... My guess is that I may of not hammered in the Balancer in far enough when I had installed it... I have a 67' 250 4.1L