Originally Posted by SS_Firehawk

Believe me, there is no way the pulley did that. It would be instantly noticeable the instant you crank your car if your pulley is having detrimental effects. A 1/8in piece of rubber is not going to be the difference between a perfectly fine motor and a destroyed one.

This looks more like over revving with bad AFR's and detonating. Causing combustion too early in the stroke can and will cause catastrophic failure. Google and educate yourself.

At least the car isn't getting scrapped, GTM FTW... And the owners wallet.