? about the 2 in a 4-2-1 header

I can't remember the technical name for the two pipes from the flange that separates the 4 to 2 in the header but my question is what is the shape/measurement from that hole? The reason I ask is I noticed those two pipes are getting kind of rusty from the ceramic coating coming off from bottoming on rocks. There seems to be a small dent in one too. I doubt that'll affect performance too much though. But I was thinking about doing a single pipe collector from the mid flange to the end prior to the cat. I have 2.5" flange and piping just before the cat. Since my cat is bigger it sits back a bit so it don't interfere with my linkage. It would be cool to have that ceramic coated but I could just use aluminized piping and thermotec wrap. Anyway, could any exhaust shop make a O2 sensor bung? That's my major concern. Has anybody else ever thought of this? What I'm talking about would be similar to a turbo down pipe I guess. It would kind of resemble a shorty style 4-1 header.
Thanks.
K

its called a collector, although i dont really get what you're trying to do..

I was just thinking of replacing the two collector pipes with just one big pipe, but I'm having doubts that the exhaust place I go to can match the DC flange shape. I'll just worry about it when my collector pipes crack or something.

o u mean u want a 4-1 header....if theats the case i dont think u can replace jus the lower part of the header u jus needa buy a 4-1

no he can make a 4-1, just unbolt the lower section, take it to an exhaust shop, get them to make the flange and weld a single, bigger pipe on. altho where it meets the flange it might be an oval so it will still collect all the exhuast instead of it hitting a barrier around the edges u know?

no he can make a 4-1, just unbolt the lower section, take it to an exhaust shop, get them to make the flange and weld a single, bigger pipe on. altho where it meets the flange it might be an oval so it will still collect all the exhuast instead of it hitting a barrier around the edges u know?

After thinking more on it, that's the same thing I figured. So I'll just leave it as is, and in the future if the collector gets wasted then I might just replace the whole header... Maybe I'll be ready for turbo by then...