Quote Originally Posted by green91
its a z6 so its obviously not an accord. seems like a dumb question to me, go ahead and replace the gasket first, a severe leak can sound like a knock at times. if the engine is knocking you're much better off replacing at least the short block since it seems you aren't very literate as far as engine rebuilding
ive never heard an exhaust leak that sounded like a knock before. usually they make 2 different noises.

but based on the OP, he knows his gasket has a huge hole. that would mean its most likely the gasket. replace the gasket and if it still makes noise, you need a motor.