Chevy Impala SS Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
10,905 Posts
I cut a 10-12 inch piece from a junkyard crossmember, shaped it to fit between the floor pan and the original crossmember with 1/8 inch clearance, then welded it to the top. Next I cut out the bottom up to the bottom of the original top of the tube, and at an angle so that the pipe has a straight line to go through. The holes in the pipe are closed by welding a couple of pieces of scrap over them. I routed the pipe straight back from the header, and made an S bend at the same place as the passenger's side, but a little shorter. I also cut the second bolt hole off of the driveshaft loop on the driver's side, and raised the attachment point in the same area (pounded it up with a hammer). I installed a passenger's side muffler hanger on the driver's side (get one from a junkyard car, the bolt holes are already there), and had the tail pipe shop put a mirror image hanger on the back of the second muffler. It required a couple of hangers for the driver's side pipe as well. You will have to get a tailpipe hanger from a junkyard car, or fab one yourself. When installing the driver's side pipe, put the transmission in low gear to make sure you have enough clearance for the shift linkage.

You can buy an already made unit for about $150, but you will still have to make the other modifications.

If you have the auto level system, you will have to remove it, because the second muffler will have to occupy the space where it is.

If you are going to put a second cat on the driver's side, you need the heat shields from an LT1 car, and you also need the heat shields with the transmission gear selector shaft and pivot from the same LT1 car. You do not need a second O2 sensor, and having a second one might confuse your computer. If you need more info, let me know.
 

·
Registered
Joined
·
33 Posts
Discussion Starter #4
I purchased a Roadmaster that my son will be delivering in a couple of weeks, so I haven't looked at the undercarriage....but I have another question.

I've read where some have put in a 3 inch single exhaust, so I'm wondering is there enough room to run another exhaust pipe from the drivers side next to where the factory one is on the passenger side? In other words, two exhaust pipes (2 or 2 1/2 inch) next to each other and exit together in the stock location? I realize that it might require special 2 in/2 out mufflers....if they exist?
 

·
Registered
Joined
·
10,905 Posts
Here are a couple of pictures of my duals. I had to make the above mods for them to fit, but they are 2 1/2 inch, and fit close to even with the bottom of the frame, so I get little scraping. I used a flex pipe, because I was starting to get on the muffler shop's nerves with all the weird bends. They are not allowed to work on cars with the cat(s) removed, so I had to supply the measurements, and was not as accurate on the left pipe as I should have been.

I have seen a frankendual on a car, and the flowmasters came from that car. I forget exactly how they ran, but it was not pretty. The pipes were 2 1/2 inch.

You could run a single 3 inch all the way back, if you are not planning to lower the car. If you are putting headers on the car, you really do not have a good choice except for true duals.

Note: The left muffler does not hit the drive shaft. The dark ring was there before I installed the pipe. The drive shaft is above the muffler when the weight is on the wheels.
 

Attachments

1 - 5 of 5 Posts
Top