3400 Exhaust Manifolds on a 3100

[3100 MPFI]

if you are asking what I am thinking, then yes, they are different in how they connect.

You can't use the 3400/1999+ rear manifold with your current downpipe. They will not line up.

If you use the 3400 rear manifold, then you need the 2000 Lumina downpipe. You also should have a custom downpipe made. I did that to my Cutlass and it was well worth it.

[Sidewinder]

Sorry, probably should have worded that post differently. I am planning on getting a new downpipe made back to a highflow cat, but I wanted to know if the exhaust manifold bolt up differently because I would like to do a 3400 swap later on down the road.

Is there any difference between the 3400 and the 3500 manifolds?

I may do headers as well, since I discovered that S&S sells them for 650.

[3100 MPFI]

I see.

IT does not matter how you do the downpipe (as long as you get it made larger and it fits in your car).

If you do a 3400 swap later on, you can use your current downpipe as long as you also use your current rear manifold.

The 3500 manifolds are totally different, and will not bolt up to your downpipe. The 3500 does not have a crossover, and the manifolds are header-style.

Here is a pic of the 3500 exhaust manifolds. This is not my pic. Taken from the post 3500 Exhaust Manifolds by onefastv6



And here is a pic of the 3100 3400 exhaust manifolds.

[Sidewinder]

Ok so I understand the differences between the 3400 manis and the 3500, but how exactly do the front 3500 manis dump the exhaust gases? Do they connect up at the downpipe? If I'm not making any sense just explain how the 3500 manis work versus the 3400, because I'm confused at how they do.

I also went onto S&S website, and I didn't know they sold headers for that price. The only time I saw them was on other websites that wanted 700 up for them, so headers may be in the picture.

[3100 MPFI]

The way the 3500 works is the front goes under the engine and they connect in the back. As you can tell, there is no provision for a crossover on the 3500 manifolds.

Now that I think about it, my brother just bought a 3500 Malibu for his bitch... er... wife. I will try to take a look at it next time I see them. They were not home today.

[Sidewinder]

That would be cool, although I highly doubt I'll be able to find 3500 manifolds. Well shall see though.

[3100 MPFI]

get them from the dealer. I asked the price of the local stealership about 2 weeks ago, and they wanted $60.00 each for them.

[Sidewinder]

Well that may be what I do. Right now its a toss up between S&S headers and Ported 3500 exhaust manifolds. I need to find out how much modification is needed to get the headers to fit before I decide though. Either way I'm sure the 3500 manis ported will help improve performance.

So 3500 definitely bolt to a 3100?

[Superdave]

Well that may be what I do. Right now its a toss up between S&S headers and Ported 3500 exhaust manifolds. I need to find out how much modification is needed to get the headers to fit before I decide though. Either way I'm sure the 3500 manis ported will help improve performance.

So 3500 definitely bolt to a 3100?

yes they bolt on and trust me, they don't need to be ported at all.. LOL

[scoopy03]

yes they bolt on and trust me, they don't need to be ported at all.. LOL

i thought the 3500 is the sister engine of the 3800

[IsaacHayes]

3300 is sister to the 3800..


Anyways I guess my post didn't stick... I was saying that check PCGUY's 3500 swap thread for info on headers and the W body bay... I think you may have to loose one front dog bone mount if you go with them.

[Superdave]

i thought the 3500 is the sister engine of the 3800

Not even close... the 3800 is a 90 degree V6 iron head...

[Sidewinder]

Anyways I guess my post didn't stick... I was saying that check PCGUY's 3500 swap thread for info on headers and the W body bay... I think you may have to loose one front dog bone mount if you go with them.

Wow that is an incredibly long thread...

After seeing the various pictures and explanations, the 3500 manifolds and how they mount makes a whole lot more sense than it did. Now I wonder is the would be more difficult and costly to make them worth it. It all depends on whether it can be done in the car...can it? Hopefully the exhaust shop I plan on going to can fab some piping. If not, the 3400 manis will be easier, but now I understand why the 3500s flow better.

Any idea how much horsepower they will add (guestimate? I know it won't be like headers, but I want to compare it if I could). I think before any of this happens though I'm going to wait and see for sure how the headers will fit.

Hopefully by the end if the summer I will have 3400 top swap (with ported intake manis), headers or ported manifolds, and a custom downpipe back to a highflow cat.

[Rhedalert]

Just so you guys know, that newer style 3400 manifold came out in 1997+ for all 3100's in w-bodies, and early 3400's in minivans (97-00, '96 was a weird one that I saw once, looks like it came from a Beretta). It really does jack shit, the only advantage is ease of downpipe installation, and it's not prone to cracking like the '94-96 ones were.

[PCGUY112887]

From what I have gathered...

2 people have mentioned putting S&S headers in a w-body car and they fit fine enough.

1 person with a monte (still a w-body) put them in and they hit the firewall a bit, so they just chopped off the flange and had the exhaust welded straight to the header. That may not be be the best solution... when I put my headers in if I have to cut anything, I will cut off the flange and have them weld the flex to the headers, then the exhaust to the flex so the welds don't crack over time.

Yes with S&S headers the front left engine mount IS in the way!



See where the exhaust manifold/heat shield goes under the mount? Well the S&S headers stick out about 1" further there, so the mount would hit it. Either you would have to just survive with 1 mount (which personally I don't plan on doing), or you will have to make something custom. I have someone that I am going to talk to about modifying that mount so the headers will fit. Basically cut out the section that is in the way, and put a big C shape of steel tubing further out more so the header will fit and the mount will still bolt on.

If you decide to use the 3500 manifolds let me know since I have a pair outside that I can get to you for much cheaper than the dealer. Just ensure that your exhaust shop thinks they can make them work. They defiantly can work, the shop just has to have half a brain to figure it out and do it.