Well, I added headers to my LO3 a while back. I got a custom made Y-Pipe made for the car. I forgot to specify the pipe size that should be used. So, for $125 I got a Y-Pipe that connects my Dynomax headers, but it's made out of 2-1/4" that runs 2-1/4" from both headers to a single 2-1/4" pipe.
Anyway, I am thinking of modifying my stock LO3 with the headers and point to a LO3 with an LT1 cam, Victor Jr. Intake, and some new heads(not sure which ones yet). Anyway, if I do upgrade the engine, should I?
A) Do like I know you'll say and get a new 3" Y-Pipe made.
B) Use the pre-exisiting pipe, except where the 2 pipes join...start from 3" there? At this point, I am going to go with this one. We'll see what happens in the future though.

 

Come on.... someone has got to have something to tell me.

 

I'd try to change it to 3" where the 2 meet.

 

flowmaster makes nice "y" pipes for about $35. check summit

 

So you both are saying that I could get away with the 2 1/4 going into a 3 then? I found the Y that Flowmaster sells. I don't know how easily I could change the exhisting pipe to add that though. I'll try to get a pic of it, but it comes in at such an angle that the pass. side pipe is prety much straight into the curve that turns to the cat.
I made up a very simple example in paint. I don't know if it explains it, but I tried. It's at the bottom of the page.
http://www.geocities.com/tzfbird/TZFBird4.html

thanks for the help though.

 

If you can't get rid of the 2.25 section by refabrication, then just get a new 3" Y-pipe. $35 is a darn good deal.

With that 2.25 section in your exhaust you are still going to have a bottleneck in the system which will hurt performance, especially with the mods you plan on doing. I originally put my headers on and kept the stock exhaust piping (except for the muffler) with some improvement. Later I went with a true 3" exhaust and noticed more improvement with minimal, at least not noticeable torque loss.

BTW, what type of headers do you have?

 

Well, I looked at the $35 thing. It's a Y that is used when making your own custom exhaust. It's not the whole thing. I would use it, but my pipes are at a larger angke than that Y. Well, I'll figure something out. Hopefully it will work out. I doubt I could lose that much power going through a 2 foot section of 2 1/4" and then into 3" but ya never know.