Exhaust Manifold/ Pipes

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Craig Childs

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Hey everyone



Does anyone happen to know what size the stock exhaust manifold outlet pipe is? I'm planning on doing a completely new exhaust and the pipes up there are looking rusty, so I think they might need replacing, and since I am already going to be in there, I will probably go ahead and take care of it all at once.



Also, I want to finagle a dual exhaust which empties on either side of the Trac (exhaust from the left stays on the left and the right stays on the right) before the rear wheels, and I was wondering if 2.5" would be too big, and whether or not that size pipe would negatively affect performance in any way.



Thank you for any help
 
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An aftermarket Y-Pipe would make fast and easy work coming off of the stock headers(or new headers, if installing them also) There is one in the swap and sell...

If not the pipes that come off are 2".



Remember that you will have to either keep the 1 Cat with the 02 sensor in it OR put 2 individual cats in with 02 sensors so there are no CEL lights.



Unless in your area you don't need them to pass inspection..:unsure:



2 1/2" pipes will be OK on the passenger side, but on the drivers side you will have the gas tank to work around. And maybe have to fab up a heat shield.



sounds like fun...best of luck



Paul H
 
Full 2 1/2 " dual pipes is a real open exhaust for a 4.0L engine. Assuming the cats are in the loop the restriction of the cat(s) will leave enough back pressure to preserve your bottom end torque in my opinion. Too wide open an exhaust tends to lead to a loss of bottom end performance.
 
Craig, all the new cats are all high flow....



I have 2.50 tails, single 3 inch in, Rt high flow can and RT y-pipe....



I would not be happier any other way....



My torque numbers on the dyno show no loss of torque..



I do agree you can go TOO big if your stock and have no other performance mods...



Todd Z
 
At that point you may be too big.....



You may need an Xcal and other things to gain the slight loss back....



Todd Z
 
those are fine.... But there is along theory of exhaust....



What is your ultimate plan with the exhaust ?? No cats at all ???



Todd Z
 
My plan is to get better sound and a decent performance gain, you know the usual stuff :) I am not looking for a huge boost, just a good gain.



I want to have two separate runs of exhaust going on either side of the Trac, both emptying before the rear tires. Although I don't know exactly how feasible this truly is because I haven't looked at the undercarriage recently, but that is what I want to do. Two cats, two mufflers, separate systems on each side.
 
IT is doable BUT the rear 02 sensor MUST be in BOTH pipes to prevent the check engine light from coming on, There are ways to shut it off also, but those require an Xcal and special tunes,



I also don't know what your emissions testing is like by you..



Todd Z
 
Thanks for the heads up, I thought about that too, so I am going to get the bungs needed for the sensors and weld them into the pipes. I live in a suburb of Houston, so it's pretty strict around here.



Speaking of which, if I just have one cat on each side, the emissions should be okay right? Pollution is already bad enough in/around the city.... that and I don't want to fail the testing.
 
if there is no law about you removing the pre cats... if the testing is strict and the look for the front 2 cats you may fail..



Todd Z
 
As far as I know, there isn't any law for pre cats, I have checked with the laws and they aren't required that I know of, and I used to work for the guy who does my inspection, and the company is owned by my uncle, so everything should be good to go.



Paul, thank you for your help

Mike, thanks for the insight and info

Todd, huge help as usual, thank you
 
Craig you cant get true duals to dump out both sides. Gas tank in the way on drivers side. I as you do live in Harris county. Best bet is to eliminate the pre-cat y-pipe for a one without the pre-cats. There is one for sale in swap and sale. As others have said for true duals you would have to add an extra main cat and wiring for the extra O2sensor. Even if there was room for true duals you would need the equalizer pipe between them for best performance. The Main cat will serve as that. We are only talking a 4.0L motor.

I have the RT-ypipe and the main converters. Single in single out cat-back(2.5"). For the dual effect you can have single in(2.5") dual out(2.25") cat back dumped behind the rear wheels or out the back. That would keep you emmisions legal in Houston. See the link for the y-pipe.

 
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