I'm going nuts

So i have a 91 olds cutlass ceira 3.3 with 141,000 miles on it. So a couple days ago i started my car at school and a knocking sound started coming out of the engine. I have replaced the a/c unit, idler pulley and the alternator. Just to make sure it wasn't inside the engine i started my car quick without the belt on and no noise so that made me feel better. But i still cant find where the knocking is coming from. I dont hear any knocking when im at speed but as soon as i take my foot off the pedal i start to hear knocking. Does anyone have a idea? Could it be the water pump or perhaps the main big pulley on the bottom(dont know what its called)Harmonic balancer? Just i cant figure out what wouldnt make noise with the belt off but it does when the belt is on....

Take a close look at the crank pulley. You may notice the rubber inbetween the the outer part and the inner part is torn or in poor shape. You may even be able to rotate the outer part by hand. If so replace it!

Take a close look at the crank pulley. You may notice the rubber inbetween the the outer part and the inner part is torn or in poor shape. You may even be able to rotate the outer part by hand. If so replace it!

Yes indeed i can see flakes of rubber coming off a little an yea i can rotate it about a quarter turn. So i will replace that today. Do i need any special tool to take that off?

You will probably need a puller and I think a 15/16 socket. Its been a long time since I have run accross one of those!!

So i finally got it done tonight and indeed it was the Harmonic balancer. The worst part was getting the main bolt off. Also to puller kit didnt have the right size bolts to use the puller so i had to go out and buy 3. But it is totally worth it having it done. Thank you all for the help:grinno: