there should be a keyway, like a groove. The balancer should have a female groove, i guess thats what its called and it slides over the crank so that it cannot spin like a wheel
I have to agree with the bigger problems suggestion. Thtas what happened to me last year. I had a keyway shear off and ended up replacing the balancer and key, problem is sometime during the shearing it tore up the end of my crank. I was able to install the new balancer without to much problem. Well, I just tightened it up and everything seemed fine. a year after that a bad vibration and then boom, the balancer brake off the crank. It ended up shearing off the crank bolt inside the crank, Motor had 200k on it anyway so it was easy to talk the wife into a new FMS crate motor. Moral of the story, check everything and make sure it is right. Stupid mistake cost me, well I got a lot mor epower to, but still. Wife was pissed when she found out I could have just replaced the crank or got a stock long block instead of the 300hp motor...sorry babe!!!!
Well thats a good thing that the key way is there.. That is pretty comon for the balancer's to just spin like that cuz the rubber rots out and gets brital.. Seen many of them do it, thats when those SFI balancers are so much better but much more expensive because their one peice rather then two peice like the stock balancer..