I am at a point in my swap where I need to figure out what I am doing for exhaust. I like the idea of the Mustang exhaust manifolds like pictured below, but have a couple questions...


First, some quick info about my setup....I will be running an 88 subframe in an 86 Fiero, F40 transmission (which will require an intermediate shaft), and my car is exempt from emissions.

What year mustang should I be looking for? I assume 94-98? Will the 99-04 fit also? If they will both fit, what is the difference between them? Are there any modifications that need to be made to them?

Every photo I have seen of them on a 3800 (I admit, I have only seen Dan's photos of them), I have only seen them on the front side of the engine....does this mean that it can't be used on the back side? Will it interfere with the axle/intermediate shaft? What about a low mount alternator?

I was looking at these: http://cgi.ebay.com/ebaymot...6QQitemZ260253165934
but was also wondering about something made for the Camaro 3800 like these: http://cgi.ebay.com/ebaymot...6QQitemZ290252130725

One concern that I have is the clearance between them and the AC Compressor. Judging by the following pic (Thanx for letting me steal all these, Dan), I am not sure if it will fit at all, let alone leave enough room for comfort.


If I were to install them the other direction like below, would the back one then interfere with the axle/transmission?

I thought those photos looked familier, the 99 up are different in the flow better but still fit with the same amount of work needed.
For A/C cars I use the one that feeds toward the tranny, it needs to also be modded to clear the starter and one piece of the block.
If you have a mig and some time the manifolds are fairly easy to use.
I have used them on both sides but only on cars that kept the alt in the stock location up high out of the way.
So far there has not been any problems with the cars I used the Mustang manifolds on which if my memory is coorect I believe it is around 10 of the swaps i have done are running these manifolds. Dan

I did some research on this a while back and found that you had to reorieint the position of one of the header connections to the head. In other words, the header end at the flange had to be cut off and repositioned. It appeared to be a difficult task as several different mods were needed in a number of locations.

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87GT - 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 09-12-2008).]

I looked at it a bit.. And figured that I would get better flow out of stock manifolds, and it would be MUCH easier to build.

quote Originally posted by darkhorizon: I looked at it a bit.. And figured that I would get better flow out of stock manifolds, and it would be MUCH easier to build.

Thats a good question. Do the Mustang headers flow much better? Maybe or maybe not. Also there are the Powerlog manifolds that according to ZZP will bolt on and flow better with no additional mods. For the cost the Powerlogs seem like the better buy.

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87GT - 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

Pretty much any manifold will flow better then the one stock 3800 one but I use the Mustang manifold mostly on 3800SC swaps using the 4 speed manual tranny to avoid the shifter mechanism all together.
With a dremmel, grinder and mig it takes only a few hours to modify a Mustang manifold to work on the 3800SC engine which I consider a reasonable amount of time. Dan

quote Originally posted by FIEROFLYER: With a dremmel, grinder and mig it takes only a few hours to modify a Mustang manifold to work on the 3800SC engine which I consider a reasonable amount of time. Dan

Care to elaborate on what exactly needs modifying?

All three ports need the mounting holes elongated to bolt on but there is lost of metal so no worries about weakening the mounting flange.
the two outer ports line up perfect but the middle port has to be cut off, turned for the bolt holes to line up and welded back into place.
I find the manifold hugs very close to the block and starter so I cut each port half way through on the bottom side, bend up the manifold to clear and weld back up the cuts I made with new metal.
This may sound like a lot but it is only a few hours work, most likely less then the time it would take to modify the shifters on a 4 speed for clearance and you are getting rid of a restrictive manifold in the process. Dan

quote Originally posted by FIEROFLYER: the two outer ports line up perfect but the middle port has to be cut off, turned for the bolt holes to line up and welded back into place. I find the manifold hugs very close to the block and starter so I cut each port half way through on the bottom side, bend up the manifold to clear and weld back up the cuts I made with new metal.

Is there any reason I can't do this to a larger degree to clear the AC compressor? Or am I going to run into clearance problems with the firewall at that point? If I can't, it appears that I need two driver's side manifolds rather than a pair. Unless I can also do this to a larger degree to clear the axle/transmission on the back side. Am I seeing this correct?

I admit, it would be much easier to see these things if I had my system ready for test fitting....but I want to know what I am running for exhaust before I start porting heads.

On swaps with out A/C and the alt up high one set from a single car will do the job but if you are running A/C then you need two driver's side manifolds to clear.
I prefer to just use the one mustang manifold and modify the other 3800 manifold to work as it flows fine and is easy to work with. Dan

quote Originally posted by FIEROFLYER: Pretty much any manifold will flow better then the one stock 3800 one

That is very misleading... The stock 3800 manifolds are not restrictive until LARGE power levels. The front manifold may look restrictive but it really is alot better than most give it credit for.

quote Originally posted by darkhorizon: That is very misleading... The stock 3800 manifolds are not restrictive until LARGE power levels. The front manifold may look restrictive but it really is alot better than most give it credit for.

So, you are saying that it is O.K. to try to exhaust three cylinders out a 1 5/8 pipe, when the three pipes, coming off the head, is already 1 1/2? Plus, the flange isn't even open all the way. The idea of a supercharged engine is flow and I don't see it, in the stock manifolds.

I got a powerlog for the front and ported the rearmanifold, the stock front manifold is restrictive and heavy..(cast iron)
At the time I thought this was the best compromise before going to headers like the Tog's or the cheap Pacesetters.

While the stock manifolds may look restrictive compared to what people UPGRADE to, they are in fact not restrictive in most mild 3800 builds, which means you wont see ANY power gains by going to a bigger front manifold suck as a powerlog, unless fine tuning considerations are involved. It even says this right on the ZZP site.

Think of it this way... The fancy big powerlog setup might be a 5lane highway, compared to a 2lane highway that is a stock manifold. During rush hour, the 2lane highway may decrease its efficiency to move that exhaust by a small margin, lets say the average speed would go down a few MPH. The 5lane power log would not see any MPH loss, but yet the cars are not going THAT much faster..

Headers on the other hand, are basically like nascar, where the lead car pulls the other cars around the track, giving you INCREASED speed. Which is why a larger header will loose power until there are enough '"cars" to lead the way.

Basically if your not a full header system, your not going to make any more power. "Flow" as you armchair guys like to call it, does not make a bit of difference when it comes to power. If a 3800 builder was ever going to mod enough to need the extra exhaust "flow" he would see a large power gain behind headers, which would be cheap compared to all the money he dumped into the mods that would benefit from the added flow.

quote Originally posted by darkhorizon: While the stock manifolds may look restrictive compared to what people UPGRADE to, they are in fact not restrictive in most mild 3800 builds, which means you wont see ANY power gains by going to a bigger front manifold suck as a powerlog, unless fine tuning considerations are involved. It even says this right on the ZZP site.

I am very interested in this thread. I just put a Plog on my engine.

I am not able to find that part on the ZZ Performance website. Would you please copy and paste it to this thread so I can read it?

Thanks,

Steve

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Steve AT 88GTP DOT com
88 GT

I like to think of it this way... if GM built it that way, all those engineers can't be wrong. Sure they get some things wrong, but they know car engines and how to tune them. The exhaust may look restrictive, but it may be tuned for the engine and those "restrictions" are there for a reason.

Just a thought.

quote Originally posted by RumbleB: So, you are saying that it is O.K. to try to exhaust three cylinders out a 1 5/8 pipe, when the three pipes, coming off the head, is already 1 1/2? Plus, the flange isn't even open all the way. The idea of a supercharged engine is flow and I don't see it, in the stock manifolds.

http://www.zzperformance.co...products1.php?id=208

They claim the gains come from the lower part being larger, but its a moot point.... If it makes consistently more power, I am willing to bet it is not really worth the cost.

quote Originally posted by RumbleB: So, you are saying that it is O.K. to try to exhaust three cylinders out a 1 5/8 pipe, when the three pipes, coming off the head, is already 1 1/2? Plus, the flange isn't even open all the way. The idea of a supercharged engine is flow and I don't see it, in the stock manifolds.

Are you forgetting that no two power pulses hit at the same time? They take turns going out the door. High performance motorcycles have used 4 into 1 stuff for ages.

If anyone wants a set of these mustang headers, I have some. I had thought of trying to use them, but the stock manifolds work in my projects well enough for the pricing I have.

Email me if interested. FastFieros@FastFieros.com

$80 includes shipping, and they are heavy. They will ship Fed Ex same day as payment made.

http://www.fastfieros.com

quote Originally posted by Steve25: I am not able to find that part on the ZZ Performance website. Would you please copy and paste it to this thread so I can read it? Thanks, Steve

That link didn't work for me.

I was hoping that you would copy and paste the verbage to which you are referring.

Thanks,

Steve

quote Powerlog Added scan this is with the front 3 cylinders skewed with 2% extra fuel. I also added 1-2 degrees extra timing and raised my Base PE by .1 (leaner).

It was discussed better in one of the main R and D threads of the powerlog.

The dyno numbers shown on the zzp site are fairly misleading due to the fact that the car HAD KR before they put the mods on.... And it is fairly apples and oranges to the actual theories i was discussing here.

I prefer the Mustang manifold for one main reason, it eliminates the cross over pipe on swaps using the 4 speed manual trannies so you do not have to mess with the shifter linkage to make it work.
The better flow is just a perk and they are easy to work with and easy to find in wrecking yards. Dan

Ok DH, got it thanks.

The Plog could be the cause of the reduced kr.

whaty year mustang are they from PM me please