Does anyone know the diameter of the outlet on the stock headers? Was assuming they are 2.25" but if anyone has a set laying around and can give me accurate measurements that would be awesome!!!

 

Any idea what the stock cat inlet diameter is?

 

No but that's irrelevant because the diameters may not match. It appears that all the used 2.25" test pipes and cats etc have soot build up around the inlet leading me to believe the header out is larger but who knows...that's the reason for my question

 

Oh ok. Figured they were the same and it might be easier to find the inlet of the stock cat vs. the header.

 

Look for the thread by the guy who pulled the trans out of his G37x to refresh the appearance. He fell down a rabbit hole which caused him to also pull his exhaust, including the exhaust manifolds, to make 'em pretty. Maybe something there.

 

Just read that the G35 DE motor has a 2.25 outlet. Not sure how closely related the two are.

Unfortunately, I'm not installing my test pipes for another 2 months. I can grab a measurement then

 

 

Looks like they are damn close to 2.5" ID...probably 2.36". Thank you very much for doing that!

 

Your welcome my. Calipers are broke but I have some new ones come in on Monday so I can get a better measurement for you then

 

 

So realistically when changing out the cats you should probably stick with a 2.5" test pipe/HFC etc unless utilizing the OEM gasket such as with art pipes. I wonder why the other companies don't use the standard set for by Nissan for that connection.

 

Yeah I don’t know why they wouldn’t stick with the 2.5 inch all the way through either.. when I ordered my fast attention type flow cats and new exhaust to make sure it was 2.5 all the way through

 

Nah some of the aftermarket pieces are 2.36 and 2.25 ID causing a step down.

I'm trying to figure out this hissing noise our exhausts make and it seems like the headers cause it. All the long tube header videos I've seen seem to eliminate the noise. I believe it's the way the flange is designed where it has the lip on the pipe. I could definitely be wrong but that's my observation.