Header performace question

kenewagner

kenewagner

Registered User
I am modifing a set of Mustang headers for my SC. I have stock manifolds on right now with 21/4" down tubes going to dual 21/2" in and 3" out resonator (had to neck the 21/4" tubes up to fit the resonator). 21/2" pipes to 21/2" mufflers out the rear. I want to fabricate new down tubes in 21/2" to match the resonator and the rest of the system. Car has almost every bolt on mod but is stock internally. Is it possible this would flow to well for the stock cam & heads at this time, not enough back pressure maybe?:confused: I will, in the future be rebuilding the engine & will go with cam and head modifacations but for now can a exhaust system flow to good?

Ken
 
kenewagner said:
I am modifing a set of Mustang headers for my SC. I have stock manifolds on right now with 21/4" down tubes going to dual 21/2" in and 3" out resonator (had to neck the 21/4" tubes up to fit the resonator). 21/2" pipes to 21/2" mufflers out the rear. I want to fabricate new down tubes in 21/2" to match the resonator and the rest of the system. Car has almost every bolt on mod but is stock internally. Is it possible this would flow to well for the stock cam & heads at this time, not enough back pressure maybe?:confused: I will, in the future be rebuilding the engine & will go with cam and head modifacations but for now can a exhaust system flow to good?

Ken
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Ken,

It won't hurt anything, but don't expect any seat of the pants power gains either. Ported stock manifolds have been proven to perform just as good as shorty headers up to around 350 rwhp. I don't think there is anything wrong with the exhaust system you have now.

I put the Kooks mid length headers, 2.5 downpipes, hi flow cats, Dual 2.5" in & single 3" out resonator, 3" single pipe to dual 2.5 mufflers on my SC when it was stock and couldn't really tell any differince except for the sound.

David
 
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David Neibert said:
Ken,

It won't hurt anything, but don't expect any seat of the pants power gains either. Ported stock manifolds have been proven to perform just as good as shorty headers up to around 350 rwhp. I don't think there is anything wrong with the exhaust system you have now.

I put the Kooks mid length headers, 2.5 downpipes, hi flow cats, Dual 2.5" in & single 3" out resonator, 3" single pipe to dual 2.5 mufflers on my SC when it was stock and couldn't really tell any differince except for the sound.

David
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Thanks david, just looking for some feedback. I didnt expect any gain now but later down the road as I continue to upgrade everything I hope it will fit right in. I am in my winter upgrade mode and this is a cheap, for me upgrade. Always have to have a project in the works.

Ken
 
Ken,

I am doing the same thing as you, I know the Mustang units are not going to show a difference right now but since I am building an exhaust this winter it will be soooooooo much easier to use just 2.5" pipe. Besides for the $15.50 that I paid for the headers it is easier IMO to cut and weld them myself rather than hog out the manifolds which have to come off anyway.
 
On a stock pre 05 v6 stang headers make quite a difference. On the 05 v6 stang headers makes quite a difference.

I have absolutely no dyno sheet as to show what headers alone will do on an SC however On most v6 Fords non supercharged and v8 supercharged it makes quite a difference.

That being said it cant hurt:O)
 
doug93sc said:
Ken,

I am doing the same thing as you, I know the Mustang units are not going to show a difference right now but since I am building an exhaust this winter it will be soooooooo much easier to use just 2.5" pipe. Besides for the $15.50 that I paid for the headers it is easier IMO to cut and weld them myself rather than hog out the manifolds which have to come off anyway.
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Yep we are on the same page about that dough and Damon I agree it cant hurt

Ken
 
DamonSlowpokeBaumann said:
Ken have you dynoed the car . Be interesting if we can get before and afte rnumbers
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I dynoed the car last spring and Dave tuned it. I am schduled to redyno with Dave in a couple of months. I dont know if that will be the only mod I have done by that time. I hope to have a few other improvments done. If I dont get my other projects done it would be nice to see what kind of improvement the headers make vs last dyno
 
kenewagner said:
I dynoed the car last spring and Dave tuned it. I am schduled to redyno with Dave in a couple of months. I dont know if that will be the only mod I have done by that time. I hope to have a few other improvments done. If I dont get my other projects done it would be nice to see what kind of improvement the headers make vs last dyno
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What did you make last?
 
Are you talking about mac mustang v6 headers, or the v6 mustang stock tubular exhaust manifolds?

On the SC I have heard that the stock v6 parts flow LESS than a set of ported SC manifolds. Plus you can port the manifolds in your driveway if you have a die grinder. Lower the front part of the exhaust, hog them out, and then bolt it back up. Can be done with a pair of jackstands.

Now if you are putting on the mac mustang headers and modifying them to fit you may get some power but I can't say for sure. A friend of mine did that on his 35th along with a rebuild, steigemeire cam, and some port work on the heads. Never dyno'd it though.
 
Where did you hear they flow less? Have you ever held a 94-98 V6 mustang header next to a ported SC maniflod? Not even close.
 
Scott Long said:
Are you talking about mac mustang v6 headers, or the v6 mustang stock tubular exhaust manifolds?

On the SC I have heard that the stock v6 parts flow LESS than a set of ported SC manifolds. Plus you can port the manifolds in your driveway if you have a die grinder. Lower the front part of the exhaust, hog them out, and then bolt it back up. Can be done with a pair of jackstands.

Now if you are putting on the mac mustang headers and modifying them to fit you may get some power but I can't say for sure. A friend of mine did that on his 35th along with a rebuild, steigemeire cam, and some port work on the heads. Never dyno'd it though.
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Modified the drivers side header this morning. I cant see where they will flow less than stock. I dont expect much diffrence right now in performace but with the engine rebuilt with cam and ported heads I expect it will show itself to be a great improvement. Here is the stock manifold next to the header

Ken
 

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You guys are smoking some GOOD stuff. lol

Seriously, do the math.

Collector size on the Mustang header is 2.5" OD. ID is 2.375 based on .060" wall tubing. So, cross section area on a 2.375" tube is roughly 4.43 sq".

Now, consider that the 2.5" tube is divided equally 3 ways, and each tube terminates at exactly the same point. Therefore the edges of each tube that are welded inside and visible from the collector end eat up the available real estate at the merge point. Subtract about .43 sq" (yes I did the math). Now we have about 4 sq" of cross section divided equally 3 ways. 4/3=1.33 sq" per cylinder.

Starting to get worried here?

If not then work the math backwards and I think you will find that the actual cross sectional area of those little triangles are equivelent to about a .85" round tube.

Merry Christmas, but I'll take my stock manifolds thanks. :)
 
XR7 Dave said:
You guys are smoking some GOOD stuff. lol

Seriously, do the math.

Collector size on the Mustang header is 2.5" OD. ID is 2.375 based on .060" wall tubing. So, cross section area on a 2.375" tube is roughly 4.43 sq".

Now, consider that the 2.5" tube is divided equally 3 ways, and each tube terminates at exactly the same point. Therefore the edges of each tube that are welded inside and visible from the collector end eat up the available real estate at the merge point. Subtract about .43 sq" (yes I did the math). Now we have about 4 sq" of cross section divided equally 3 ways. 4/3=1.33 sq" per cylinder.

Starting to get worried here?

If not then work the math backwards and I think you will find that the actual cross sectional area of those little triangles are equivelent to about a .85" round tube.

Merry Christmas, but I'll take my stock manifolds thanks. :)
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Dude, you have way too much time on your hands!:D But that makes alot of sense. I email Wynn ealier to see if he has any manifolds ready, too poor to do my own.
 
Crack is currently being smoked nationwide.

Take a good look at the SC manifolds...A real good look. ::shakinhead::
 
You forgot something. The pulse of the exhaust is handled at a different length in the header then in the manifold. Take a look inside. That should help out too. But when it comes down to the nitty grit, the math is never wrong.

Chris
 
I'm gonna be installing my 95 mustang units, as I cannot believe the Mustang units flow any worse than the stockers by looking a them side by side.

The length of the tubes seem to me that it would straighten out the flow and incease velocity.

But i haven't stayed at a Holiday Inn Express recently, so perhaps I'm totally off, and wrong.

I gots to go see Dave at the dyno next month (Dave you still comming ot the ATL???), so perhaps I could do a before and after stock SC and 95 stang manifolds (mine were jig moded by Wynn, thus repeatable).

I don't know about the likelyhood of such a thing, but perhaps if someone else can pay for the extra pulls, I might could dyno both of them same day same mods, but I'd have to get an extra hand to help me swap em out...

I was already planning on using some flexible exhaust pipe to hook things up for the trip to the mufler shop. I guess I could leave it that way for a spell.
 
In the end you can consider the SC manifolds as a 2 inch ID (maybe) Log type header. Not much roomfor flow there There are however many reasons why a real header will generaly outperform a cast iron manifold. And no one header/manifold will be ideal for all applications. Truthfully the only way to see exactly what will be gained is to do an immediate before and after dyno test. Ultimately the 2 inch collector which is so close to the exhaust ports is what kills the factory manifolds.
 
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