One of the most common questions I get asked is "what mods are necessary to fit the 4th gen SE exhaust on my 3rd gen?" The draw of this system is that it is inexpensive. Actually less expensive than buying raw material and building a system from scratch yourself, and you have a great starting point!
I think first it's important to understand that the system is built for a 93-02 car. The 3rd and 4th gen cars are identical from about the torque arm mounting area back to the bumper. However, in front of that they are vastly different. The subframe coming down from the firewall to the transmission crossmember diverge in opposite directions between the 2 generations. The 3rd gen subframe rails diverge inward, towards the transmission and the center of the car. the 4th gen diverges outward, towards the rocker panels. For this reason, the area between the header collectors and the x-pipe must be modified.
I'm going to show pictures of the full to-the-bumper system, but the concepts are the same between each as they both have the same problem.
Here is a 4th gen and this is installed as designed/out of the box directly from speed engineering.
Here is an example of the system installed on a 3rd gen. As you can see the area between the header collectors and the x-pipe has been cut down to better fit the contour of the 3rd gen subframe:
Both of these cars are t56 cars, but the concept is similar for an automatic as well, you just have less room to work with as the pan rails get pretty close to the subframes, especially on a bigger trans like a th400 or 4l80e.
I also think it's important to point out that you do not have to be using an LS engine to benefit from this system. These concepts could easily be applied to any engine combination running a long tube header with about the same outlet location. You also do not need any fancy tools. Anyone with a chop saw and a welder can handle this job.
Video of a recent system install that I did can be found here
If you're ready to dive into your own install, grab a "to the bumper" kit here:
or an "axle dump" kit here:
Happy Hotrodding!
-Matt Walter