3400/3500 top end swap on a 2.8

[Tonglebeak]

Ah 3100 downpipe...ok. I assume the ports will match once everything else is replaced correct?

I'll probably take this guy up on his offer than. And yes, he's including both sides for the exhaust manifold as well as the 3400 xover pipe. I'll see if I can get a 3100 downpipe as well, although of course the cieras were no longer made after 1996. From what I've heard the downpipes between the 3.1 ciera and the 2.8 are the same. Who knows :\

[3100 MPFI]

3.1 and 2.8 are the same engine. A 3.1 MPFI is just a STROKED 2.8

This is the 3.1 in my 1990 STE. As you can see, it looks the SAME as yours, only it say 3.1 instead of 2.8.



The 2.8 and the 3.1 are GEN 2 engines. The 3100/3400 engines are GEN 3 engines.

The 1996 Ciera will have a 3100, so the downpipe should fit perfectly in your car.

THE ONLY THING TO WATCH OUT FOR.....

There is 2 different rear exhaust manifolds, and the downpipes are NOT interchangeable. As long as the rear downpipe is the same as the rear manifold, there will not be a problem.

One of the rear manifolds has the downpipe off to the side, and one has it in the middle of the rear manifold. Make sure that the downpipe is the same as the rear manifold. I THINK that your Ciera will need the SIDE EXIT manifold. I will see if I can find a pic of the side, and the center exits. That way you can find out which you need.

[3100 MPFI]

This is the early style 3100 rear manifold.


This is the later style 3100 rear manifold.


You need to determine which yours will need. You will probably have the top pic. I mean, that is what the DOWNPIPE for your car will be for.

Something else you are going to have to look into is the EGR. Right now, you have the vACUUM EGR. You are probably going to need to upgrade to the DIGITAL EGR, and get a different computer for your car. That is something we can cross AFTER we get to that bridge.

If you get the LARGE PORT 3100/3400 upper manifold, you will need to get an ADAPTER for the EGR.

As I keep saying, there is a LOT to take into consideration. I strongly suggest getting the parts first, and then going from there.

Is your tranny VACUUM controlled? You will need the vacuum pipe for it.

[Tonglebeak]

Yes it's vacuum controlled. I don't even use my EGR valve so it doesn't matter to me as far as that goes. On Thursday I'll actually have time to get pics and things together. Unfortunately I wake up and go to work, and by the time I get home it's dark.

I'm almost positive I have a center downpipe, but I need to double check. How can you tell the difference between a large port 3400 lim and a regular one?

Also, 86euro on a-body.net mentioned that I'll come across issues with my throttle cable and throttle valve cable, when trying to hook them up to the 3400 throttle body. Although if I decided to use a 3500 throttle body...gah, I don't know >_>

[3100 MPFI]

I think all of the 3500's are drive by wire..... ELECTRONIC throttle bodies. There is no cable. If oyu use the 3500 upper intake manifold, you will need to get an adapter to use a different one.

I think you can just get the cables out of a 3100 Ciera, and swap out the linkage on the throttle body. That is what I did. I had a minivan throttle body (when I did the intake swap on my 1996 Grand Prix), and I just pulled the minivan linkage right out, and swapped in the stock Grand Prix linkage. Worked fine. I also did that to my throttle body in my 1988 Cutlass Supreme (swapped in 3100).

It does not matter what downpipe you have NOW. It will NOT bolt up. They are angled differently. You will need to get a downpipe from the 3100 Ciera, and swap it in, then make sure you have a rear manifold that it bolts up too. You might have a center outlet now, but if the 3100 Ciera downpipe is SIDE, then you will have to have a side outlet. They are pretty cheap on EBAY.

If you get a new enough upper intake manifold, then you can get a block off plate if you don't plan on using your EGR.

As for telling apart the lower intake manifolds, just look at it and count the number of BOLT HOLES to hold down the UPPER intake manifold. The older has 12, and the newer has 6. Also, on the ends, it will be stamped with the YEAR. 3400 does not matter (they are all large port), but with the 3100, it will be 99 or newer.

I will see if I can find pics of the 2 different lower intakes.

Might also be an issue with one of the cooling pipes. Have to do more research.

[Tonglebeak]

Regarding the 3100 large port heads: are they the same size as the 3400, or do 3400 heads have even larger ports?

Like I said before, I will get you many detailed pics of my engine compartment on thursday. If there's anything specifically you needed a picture taken of, please let me know. I really do appreciate your help in all of this.

[3100 MPFI]

Here are some pics:

1999+ 3100 and ALL 3400 UPPER INTAKE (large port):


1993-1999 3100 UPPER INTAKE (small port):


1999+ and ALL 3400 LOWER INTAKE (large port):


1993-1999 3100 LOWER INTAKE (small port):

[Tonglebeak]

Ok cool. What about the heads...are the 3100 and 3400 heads the same thing? Or are 3400 heads larger as well

[3100 MPFI]

Depends on years, etc.

In my 1996 Grand Prix, I was able to get the larger port lower intake to bolt right up. The only difference was 1 alignment tab. I just ground off the middle one (That didn't line up), and was good to go.

1993-1995 heads have the STAMPED STEEL rockers, and will require doing some minor modding to the intake for it to bolt up. The rockers will hit the lower intake on those heads.

The 1996+ heads have ROLLER FULCRUM ROCKERS. The intakes will bolt right up.

I want to say that the 2000+ heads have larger valves, or something. Can't remember the exact specs and years, but like 2000+ 3100 and 3400 heads have larger vavles, or something.

Everything pretty much bolts up, but any questions you have, you can always ask.

[Tonglebeak]

Alright. I was just wondering though, if you lay a 3100 head next to a 3400 head of the same year, does the 3400 have larger valves than the 3100 or are the valves the same size between the two?

[IsaacHayes]

3100 2000+ is same head as 3400. older then no, smaller valve.

[Tonglebeak]

Ok thanks.

[Tonglebeak]

Quick question: does the 3500 upper intake have any advantages over the 3100/3400 UIM? What about the 3400 over the 3100?

[3100 MPFI]

large port 3100, and 3400 are the same. There is no difference other than the 1 and 4.

As for the 3500, it is a shorter runner (well, no runner at all really). I think that increases BOTTOM end? Someone clarify that for me.

For you to use the 3500 top, you need to do more work. The Fuel Pressure Regulator will hit, so you need to grind some material off, and then you need to rewire the MAP sensor. You will also need a throttle body adapter.

I recommend sticking to the 3100/3400 for now, and go to the 3500 later one. After the car is running good.

I think you might have to tweak the tuning once you swap that out, especially if you keep the lower displacment of the 2.8 I have NO IDEA how your engine will react, but Ben can tell you I threatened him that I would destroke my 3100 to a 2800 if he harassed me too much about rebuilding my 3100 instead of getting a 3400 or 3500.

[bszopi]

Shortened runner length improves top end performance. Long runner length helps low end torque.