I have a 02 civic dx. The cat is connected to the exhaust manifold. I just put a header on it so I have no cat, and its making an extremely ricey sound. I was wondering if it is because I don't have a cat, or could it be that the exhaust is leaking where the end of the header connects to the exhaust pipe?

Also, I just used the old exhaust manifold gasket, is that a real issue?

Any insight would be helpful, thank you.

P.S. the header isn't for gaining 100bhp, I know I'm driving a Honda civic, my manifold just cracked down the middle.

 

You can check for leaks by temporarily blocking the tailpipe with the engine idling. It should just quietly build up pressure. If there's a leak, exhaust will hiss out of the leak.

A cat converter has a considerable quieting effect as well as of course getting rid of pollution. I would suggest installing an aftermarket unit (make sure it's a real converter, not the ebay ones that are just an empty pipe) after the header.

 

Ok, thanks. I'll put a cat on and see how it goes