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Exhaust Manifolds

75K views 282 replies 42 participants last post by  peva 
#1 ·
Group,
As many of you know, we have all been looking for way to get rid of the stupid design of the OEM exhaust manifolds on the 3.2/3.5's. I personally have tried LX manifolds to no avail. Others have tried LX headers only to compromise the gains by the ridiculous bends that are needed to accommodate the headers. Well, I am going to try to take a trip back in time (so to speak) I have recently acquired a set of 1G 3.5 exhaust manifolds. They are a traditional design, and I think they can be plumbed in to work in our cars.

Here, feast on some pictures...

First off, here are the OEM 2G exhaust manifolds..



Below the manifold is a header that a former member of the 300M Club made, his alias was "Gallotte"

The manifolds as I received them....












After a little media blasting...











Next will be Catalytic Converter selection

Any thoughts??
 
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#4 ·
what is the design flaw behind the 2nd gen exhaust manifolds?
 
#6 ·
I will be following this for sure.
 
#9 ·
What my thought was about the converter placement is this, come out of the manifold with a 45* bend, then place the converters. There should be room for a smaller, high flow converter in that configuration. It will allow for the O2 sensors to be nearly in the same location as the factory configuration. With them being further back, and down in the engine bay, heat should be less of an issue.
 
#15 ·
this is where you may run into a problem,, the main reason the put the oe cats so close to the engine, is so they light off faster, thus lower emissions, ok, if the ECM dont see a change into closed loop in such and such a time it will toss a code,, usually a po420 or po430, hoping Im wrong,,,
 
#10 ·
I've pondered doing this as well Tom. Just curious if using the factory 1st gen cats will work better molding to our factory pipes or to buy aftermarket ones?? Making nice progress tho I'm watching this thread for the end result! Pics please!
 
#13 ·
When I head up to Indy Monday, I am going to stop by and see my exhaust guru to see how much it will take to get this done. And, if we can reuse the factory converters or not. I would prefer to use them, but we'll see.
 
#16 ·
Its either these work or the custom headers I am having designed do. It would be a lot easier if these work though, The cats will only have to be moved 7-10" back. Having seen the cats out of the car there is plenty of pipe there. Should be as simple as cut and re-weld. To bad I sold the set I had.....
 
#17 ·
I think it will work too, maybe not with the factory converters....but with shorter, smaller ones.
If you put a 45 degree bend at the end of the 1G manifolds, that is what will make it all possible.
 
#22 ·
Well, my exhaust guy and I discussed the manifolds today, and he can do it.
We are going to have to get 2.5" converters, and move them down into the tunnel, and also extend the O2 sensor harness ~ 36" - 40"

Having the converters out from under the hood will lower the under the hood temperatures considerably.
Doing this will also have the least amount of impact on the rest of the exhaust system
I will begin my hunt for suitable converters...
 
#23 ·
I have always wondered this, will the O2 sensor operation be effected by extending the wires? But, I just looked and it turns out they make O2 harness extension harness's so I guess it isn't. Since you're now putting them in the tunnel couldn't you just re-use your stock cats and just offset them from each other so they are still parallel to each other? Anyways, it's good to hear that they will work.
 
#27 ·
Looking like a good project, Tom.

I had heard about using 1st gen 3.5 manifolds on the 2nd gen cars, but I never remembered seeing anyone complete it. I hope this turns out for you, I like it so far.

So, you're going to keep your x-pipe, cherry bomb glass packs, and cherry bomb turbos, all at 2.5? I can't remember - what did you do for the center cat?
 
#29 ·
It is looking like the Cherry Bombs will be lost, and the converters will be put in their place. Everything else will remain the same.

I'd love to see pics from underneath once you get it done, I want to see where you end up with the cats and what you use. I think the first gen manifolds are the answer, they look like they will flow better, hoping they do. I'm trying to envision how you will fit two cats side by side in the tunnel thats why I'm so curious to see pics. That would be awesome too to get some of the heat out of the engine bay. The shape of the first gen manifolds too make them easy to wrap with header tape, it's a lot less expensive than jet hot ceramic coating and pretty effective. Would be a lot easier to wrap than the 2nd gen pieces.
4" diameter cats will fit side-by-side in the tunnel with no issues.
 
#28 ·
I'd love to see pics from underneath once you get it done, I want to see where you end up with the cats and what you use. I think the first gen manifolds are the answer, they look like they will flow better, hoping they do. I'm trying to envision how you will fit two cats side by side in the tunnel thats why I'm so curious to see pics. That would be awesome too to get some of the heat out of the engine bay. The shape of the first gen manifolds too make them easy to wrap with header tape, it's a lot less expensive than jet hot ceramic coating and pretty effective. Would be a lot easier to wrap than the 2nd gen pieces.
 
#31 ·
The further away from the engine you get, the less heat you have in the exhaust gas to light off the converters. As it is, I am moving the cats ~ 36" further downstream.
 
#37 ·
Otherwise than what you've indicated, there is no problem with fitment then with the 1st gen manifolds? All you need to do basically is a couple pipe bends coming off the bottom of the manifold and relocate the cats. Before I rush out and hunt up a set I want to make sure they will fit with no other mods.
 
#40 ·
Technically speaking, it will work with using the factory converters, I am going to replace them with a style of spun converter with the O2 bung welded into the body of the converter itself. Getting it as close to the catalyst as possible, where the increased heat from the catalyst reaction will help with the readings. The manifolds will physically fit, no problems there.
 
#38 ·
Bob - if you don't get any manifolds by the time I get my 3.5 motor out of a junk yard, I'll have an extra set to ship to you... but it will be Spring, uh, springs.

Tom - seriously, if you want, I'm sure there are lots of us that would slobber that extension harness together. I'd do it for ya.
 
#39 ·
Bob - if you don't get any manifolds by the time I get my 3.5 motor out of a junk yard, I'll have an extra set to ship to you... but it will be Spring, uh, springs.
Would that be spring in ND or spring in FL, which is in about two weeks? Seriously, I wont be ready for them for a while yet anyway so I may take you up on that offer. PM me a price when you get em. Thanks. BTW when does spring come in ND?
 
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