What would I have to do in order to have true dual exhaust? I'm swapping in a 4.0 from a 92 ranger (only 60k miles) and I'll be putting in a new cam, it will be ported and polished and port matched to gaskets, new gaskets, headers, chip, and within a year it will be supercharged as well. I'm not holding back (ok well.. I am.. but not much!), and I would also like to run the true duals. Will this be possible with the undercarriage? I want to have an x-over with Flowmaster 60's on it.. no cats. How much should I expect for a shop to do this?

 

The biggest problem I can see is the O2 sensor. Does the 4.0L have one on each side or just one that reads all cylinders? If it's just one then your system will only be reading half the engine with true duals. You might want to look into a nice set of headers like from headman that include the Y-pipe($220.00). Great flow and if you split it right after the Y could consider it a dual system with a close cross-over pipe. I know it's not what you wnated but the computer will be happy and you'll get better torque.

 

O2 sensor would be an issue. The only other issues for true duals with crossover pipe is your front prop shaft and the crossmembers under the transmission. I have seen some exotic workarounds for these issues on the BIIs, Rangers, and Explorers for engine swaps, though... so, it's not totally impossible. It's just going to take some fabrication by a really good shop (or buddy with the equipment and skill). Generally, though, the aftermarket and stock exhaust crossover is adequate. You can run hi-flow dual inlet / single (or dual) outlet cat and go from there. With the single outlet cat, you can run a fairly large diameter pipe -- usually 2 1/2" -- to a single inlet / dual outlet muffler and then to dual pipes. This can also be a bad thing, though -- unless you downsize your outlets -- depending on what you do with the engine. In your situation, though, you could probably go with 2 1/2" pipe from the cat back.

 

If you used a '93 Cali or a '94 computer (and associated emissions components) instead of the '92, you'd get dual O2 sensors (left and right sides). That would resolve the issue with a single O2 sensor system.

 

Well the headers come with a Y pipe already, I was hoping for true duals for the sound and everything. But I think just having it split after the Y-down and O2 sensor would be fine.

 

You can run the O2 sensor in the y pipe with no problems by welding in a bung if you need a single sensor. It comes this way stock on some vehicles.

As for the true dual, you can do what I did. Give the BII a 2" body lift. Run a 2" exhaust pipe straight back along the wheel well area (not over the gas tank!) and exit between the body and rear bumper. Obvious, the plastic valance panel has to go, you can use it as a template and cut yourself a sheet metal one instead.

I did it this way to keep my exhaust out of the water after I drowned my BII one time and to keep the exhaust from getting hit off road. Still, it might work for you too.

 

So you ran it in the rear between the bumper and the hatch? That plastic valance? Do you have pictures of this?