My first post, searched but still have a question. Recently got a 89 firebird formula, 305 TBI. I'm looking to put headers and new exhaust. From what I've learned on here, I need a three inch but the headers I've been looking at (leaning to hooker 2055) all have a connector/Y-pipe with a 2.5 inch dia. Doesn't it defeat the point of 3" when you only have 2.5" feeding into it? Thanks

 

2055s are good, 1.625 primaries to a 2.5" collector then run 2.5" pipes off each cylinder bank and merge into a single 3"

 

However, the collectors need to be fixed because they cone down to 1 3/4".

 

Yea, I never understood the design of the 3/4 length headers that they make for these things. I had a set of old headman's that I've had since 91 or 92 (before they made them with the ball and socket flanges, the PN still exists but I don't know if you can still buy them), cut off the collector flanges, blasted them and welded on some stainless v-band flanges:


Coated them


and then grabbed a newer ball and socket y-pipe for the current ones, cut it up, added the 3" v-band flanges to mate to the headers, made them fit the flange locations for the older headers, cut off everything after the Y that was smaller than 3" and made my own


Now I have 1-5/8" primaries, 2x 2.5" into a single 3" that fit tighter than the stock exhaust and don't touch anywhere (though the driver's v-band flange is really close to the k-member). Up above the oil pan/K-member:


Up above the sub frame rails (and I checked there is still room to snake some subframe connectors in there without touching):


If I was going to do it again I'd probably use the new, ball and socket version of the same headers and do the same thing to the y-pipe, it should be less work.

 

Thanks! I was out of the car game for a long time thanks to an extended stay in Japan compliments of Uncle Sam so I missed a lot of changes that went on in the 90's. This site is a gold mine.

 

It's hard to tell from your fuzzy pic but it really looks like it's about 2" and it's because of the way you're holding the tape measure. Since exhaust tubing is sized by OD I doubt that it really flows less than a 2-1/4" pipe, and IRL I would wonder if it's anti-reversion affect would cancel the restriction that it presented.

That being said, if I saw that i'd probably hold the other side of the ball and socket, socket up against it, mark how much it covers and cut off any excess off that cone.

 

Thanks. I ordered the 2055's ceramic coated with Y pipe and the cat back system, Summit had them on sale. Now just have to figure out what cat to get.