I have a 00 civic, can a crack in my exhaust manifold cause my engine to to
 

Make a knocking sound? ? I just replaced my engine 2 months ago. I have a crack in my exhaust manifold, but have not replaced/or fixed it yet. Recently my engine started making a knocking noise. It gets louder and violent when i give it gas. Can that be from my exhaust manifold? Or is the engine that i had put in no good? Please help