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I have a general exhaust smell (also likely burning oil from a valve cover leak I’ll be fixing) while sitting still with my blower on and set to fresh air, and I have pretty disappointing fuel economy even after putting in a brand new O2 sensor, so I was looking to replace my exhaust manifold. The aftermarket ones I was looking at on rock auto etc seem to be in the range of $400, but there are several manifold/cats on eBay for only $100.

Wondering if there was some negative to these super cheap units as far as performance/life/not being a direct drop-in etc. or if they really are just a good cheap option that work well enough.

Also another engine question- I have a pretty pronounced clacking from the engine during acceleration, didn’t know if there was anything specific I should be checking. Planned on replacing the spark plugs during the valve cover replacement, saw another posting that mentioned checking valve lash if you had this kind of noise.

 
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does the ebay ones have the cat? rock auto ones would
EX exhaust system is different, look for DX/LX!!!

 
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Yes there’s a whole class of listings for civic cats under $100. This is one example but there are dozens. Didn’t know if there was some kind of gotcha or if these would do the job.

eBay Cat

 
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if you have emissions testing where you live, I would recommend not getting the cheaper ones.
have you removed the manifold to check if it really need replacement?
you can also smoke test it. throw smoke and see if smoke is being displaced around the manifold

I do vape, so I use my vaping device...

 
Rep Power: 366

depending on the age of your cat, it could also be clogged.

https://www.google.com/search?q=clog...h=684&dpr=1.25

 
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I do have emissions, but it would just be an OBDII scan and not an actual exhaust test. As long as it doesn’t throw a code and can be visually confirmed as being in place I would be good. I’m not actively trying to ruin the environment, but at the same time if I can fix this and I’m personally breathing in less exhaust everyday, that’s the choice I’ll go with. At $400+ I would likely not consider a fix at all.

I like the idea of using smoke as a way to check, I don’t vape but I’m sure I could find some other source of smoke or vapor. If the header really is this cheap I might just want to go ahead and do the replacement rather than spending hours hunting microscopic hairline cracks in the system that open or close based on temp. though.

 
Rep Power: 366

just be aware that cheaper can cause other problems later on, requiring you to buy another part, thus more expensive in the end

 
Rep Power: 222

Did you put a proper OEM o2 sensor in.
cheap aftermarket cat will probably throw a code within a year