Is there a special size for removing the cat to install a test pipe? I was able to get the cat to exhaust bolts out easy(14mm) but the headers to cat sping bolts I can't find anything to fit the nuts. Everything I can find says its a 12mm which does fit the bolts but is too large for the nuts, don't know why they'd be 2 differnet sizes. Am I missing something here I've tried just about everything and nothing fits. It's a 2005 if that makes any difference, any help would be greatly appreciated.

 

I don't remember much but I think I used a deep socket for the nut side. Try that. Maybe your socket isn't sitting on the nut.
If you don't have a deep socket. Take the socket off and place it on the nut. Then put the ratchet on the socket but not in all the way.

 

If they are oem Honda nuts they should be 12mm, unless someone put on a smaller nut in the past, like a 10mm or 11mm, or perhaps an SAE size like 1/2 inch ? I am doing my cat right now so I am familiar with the sizes on mine.

 

Ok, I'll give it another try again tomorrow, but I had already tried the 12mm(too big) and an 11mm(too small) also tried the sae equivalent. This just really confused me as I have a lot of mechanical experience, maybe it was the cold lol.

 

it should be the 12mm if its oem.

 

If the 12mm is too big and the 11mm is too small then it's probably stripped.

 

Yeap, it's probably stripped.

Get yourself some vice-grips and go to town, then head over to a parts store and grab some new bolts.

 

You have a lot of mechanical experience and you're having trouble finding a socket or wrench to fit a nut? I'd get some rest and breather and try again...

P.S. If you still can't get it, vice grips. If you need to break it loose, wd40/equivalent, vic egrips and a small sledge (3-5lb).

 

Those bolt extractors from Irwin are a godsend. Removed a stuck oil drain plug and corroded cat-to-header bolts on various cars with ease when none of the above methods worked.

 

^ They're also called "Turbo Sockets" and they work even better when they're on an impact gun, but not everyone has access to air.