If you could make better headers

Jason Wild

Registered User
Like it says if you could make a better set of headers what would you do. I'm looking at doing my own set of mid lenght Headers since I have ever thing you need to do this.
 
Jason Wild said:
Like it says if you could make a better set of headers what would you do. I'm looking at doing my own set of mid lenght Headers since I have ever thing you need to do this.

Try to make your collectors aerodynamic and as small as possible.
 
Dave,
Something like 15/8" collectors would be better then the 13/4" on what you can buy now. Is something that is 100% equal length that much better. I know there is this good post from wayback when with a lot of info over on the old TBSCEC. here is the link
 
Jason Wild said:
Dave,
Something like 15/8" collectors would be better then the 13/4" on what you can buy now. Is something that is 100% equal length that much better. I know there is this good post from wayback when with a lot of info over on the old TBSCEC. here is the link

What you are talking about is the primary tubes. The collector is at the and ties all the tubes together right before the exhaust system starts.

What I would do is go with 1 5/8" primaries with 2 1/2" collectors. Now as far as equal length or not it all depends what part of the power band you are trying to improve.
 
what was I thinking about at the time I dont know. To much home work.
I want to kept the low end TQ as well kept it all the way up to like 3200RPM like it is now but at the same time let me have good HP in the top end.
 
Primary tubes 1 5/8" dia. 36 1/2" long with collectors 2 3/8" dia. and 13.5" long would be a real good start. ;)
 
36 1/2" sounds like a long primary tube but I guess it might not be all that bad. time to start working this all out.
 
Jason Wild said:
Like it says if you could make a better set of headers what would you do. I'm looking at doing my own set of mid lenght Headers since I have ever thing you need to do this.

I would make them avoid the steering shaft so I don't have to bash them with a big hammer :D

3" collectors would be a good idea also and the flanges should also have a raised bead on the inside for a better seal.
 
Jason Wild said:
36 1/2" sounds like a long primary tube but I guess it might not be all that bad. time to start working this all out.

Longer than commonly seen primary tubes and collectors are needed on an SC due to the relatively low RPM at which the engine makes peak torque and horse.

Most of the off-the-shelf headers for V8's have primaries and collectors that are far too short in the 26-28 inch range. A length that wouldn't "tune" until something over 6500 rpm in most instances.

Rough rule of thumb is lower RPM=longer tubes/collectors and vice versa
 
Actually that is only partly true. The tuned frequency of the pipes has to do with both the diameter and length of the pipe. A larger pipe will be shorter than a smaller one when tuned to the same frequency/rpm. Therefore it stands to reason that a 15/8 pipe 36" long will have a tuned frequency the same as an 1 3/4 pipe that is significantly shorter. Most long tubes are tuned for around 4500rpm. If you tune the header too low, it will become a restriction at higher rpm. If you tune it too high, then it becomes very "peaky" and has no midrange power. Most longtubes are designed to improve mid range power without sacrificing top end.

Thus it is that with all other things being equal, properly made shorty headers will make just as much HP as longtubes, sometimes a tad more. The difference is that the longtubes will kill them in mid range power and will be faster on the track.

Longtubes on an SC are kind of an enigma. You can tune the headers for the 3.8 in N/A form, but that would end up with a restrictive design for high boost/high rpm applications. A longtube header is going to be most effective on your motor when it is running N/A (or in other words, part throttle). If you tune them for boost applications, they will be too big to help you in part throttle situations, and be of no help under boost since the SC takes care of scavenging the cylinders anyhow.

What you have to understand is that the primary purpose of longtubes is to present a negative pressure wave at the chamber in time with the drawing in of the intake charge. In order for this to work effectively, you must also have overlap in your cam grind. Stock SC cams do not have this so the effect is minimized. Even if you do have a cam with overlap, then the negative pressure wave is only helpful if you don't have 15psi cramming air into the cylinder anyhow. See where this is heading?

That doesn't mean that they can't be beneficial, but it does mean that they are not going to be beneficial in the manner that longtubes are traditionally useful.

So what purpose do the headers serve in a boosted application? Well, there is a science to simply scavenging the exhaust gasses without trying to draw in fresh charge from the intake. While this is certainly a lesser effect of a good header design, it is still worth pursuing. Thing is, it does require a different set of equations than are used in an N/A application. Sorry, I can't give you that information (I don't have it, lol).

The reason for a small collector is that with only 3 pipes entering the collector at once, too large of an open space will take away from the scavenging effects of the collector and render them useless pipes. If you could triagulate the ends of the tubes so that they merge together in a smaller space, that would be very helpful....

I'd definately want a 2.5" collector. I'd run 2.5" from the primaries directly into a 3" Y (approx 12" long) and then 3" back to the rear and 2.25" pipes out. Hmmm, did I say that? I think that's what my car has (except for my sloppy 3" collectors :(). lol
 
I dont think scavenging really works all that well on supercharged applications whne talking about headers...Maybe a tad when off boost.

Also all the header theory (which we just clipped the tip of the iceberg with) is all fine and dandy..However it tends to confuse most..

Now back to the factyory stock exhaust manifolds.... Why does a swap to headers on a 4.6 DOHC cobra make a substantial gain while on the SC most have claimed little to no gain...

Cant possibly say the stock exhaust manifold is not restrictive:O)
 
Simple really Damon, non of the headers sold for the SC are designed and built right(wrong dimensions). However the new long tube Kooks come closer to being right than anything else thats been made so far. The stock manifolds work decently inspite of themselfs and that certianly is'nt a testamonial to there great performance abilities. Tuned headers work from manipulating sonic waves as Dave has mentioned, what that has to do with if the engine has a blower on it or not is beyond me. I know that non of the big exhaust guru's(I mean the real guy's that pioneered tuned exhaust headers nor the data and experiments they conducted) believe that a blower changes the physics involved in tuned headers. I keep hearing that the blower scavenges the engine and thats just plain wrong. The blower just crams more air into the motor and if you dont address the exhaust side of the engine you still get intake charge dilution with exhaust gases. The blower has nothing to do with the exhaust side of the engine, we are talking about a blower engine not a turbo engine. Turbocharging does play a role with the exhaust because its in the direct path of the exhaust.(but thats a whole different discussion)
Cramming more air into a 4 stroke engines cylinder while the exhaust valve is closed does not help to expell any remaining burnt exhaust gases,(and thats all a blower does) there trapped. The best thing to do is get the burnt gases out when the exhaust valve is open by manipulation of the sonic waves because thats how it works on every internal combustion engine ever made(research has provided undeniable proof of this) 2 stroke or 4 stroke it makes no difference. Research conducted has proven that a collector on a header that is as small as 1/8" in diameter larger than optimum can cause a loss of 50 ft lbs of torque. Maybe thats important to the user and maybe it is'nt but it sure proves that bigger is not always better.
 
Mike, lets for a moment focus on only one aspect of a tuned header.

It is my understanding that one of the big benefits of a tuned pipe is that it induces a negative pressure wave (vacuum) at the intake valve during the point of overlap. This is a critical time as it marks the beginning of the acceleration that draws the new charge into the cylinder.

I have been led to believe that this "suction" effect provides much better cylinder filling at the tuned rpm. I have also been led to believe (and common sense follows) that a supercharger or any charge pressurizing device negates the effect of this phenomenon on cylinder filling. It also stands to reason that if your cam does not have any valve overlap then this effect is mute.

It also follows reason on a naturally aspirated application, that if you have a very large amount of overlap and header that is tuned too low you will actually draw the fresh charge right out the exhaust. I have understood that this is one reason that and exhaust system of sorts will often times help a race car run faster. Because the headers are actually drawing too much air and cheating the cylinder of a full charge.

Am I misdirected in assuming that this aspect of header tuning is a large part of the equation and am I wrong to assume that the supercharger negates this particular benefit?

Is that 1 5/8" primary pipe ID or OD? And where exactly do you find 2 3/8" pipe anyhow?
 
For cam over lap,or reversion of exhaust air can be somewhat takin care of
with proper built headers.As black as SC combustion chambers are ,I would say this may be a problem.If you look at the floor of the exhaust port on a STEG head.
he does weld build up for the exhaust floors.To raise the radius for better flow.And he leaves the mouth floor of the exhaust header flange straight across the bottom.this is for reversion.

To make a header that works best all across the RPM range (daily driver).You will have to compromise.

The best header is purpose built.One header for each job.

If you build headers,I would want them to be coated with a heat barrier
and shiny.

Randy
 
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Dave now I understand where and why people dont believe in tuned headers on a blower motor. Thank you for your honesty and explanation because when I've asked people in the past to explain why they think what they do about the subject I usually get called names or just ignored. I'll disect your post with quotes from you and try my best to explain whats incorrect in a way that prehaps everyone will understand. Here we go:

Dave:
Mike, lets for a moment focus on only one aspect of a tuned header.

It is my understanding that one of the big benefits of a tuned pipe is that it induces a negative pressure wave (vacuum) at the intake valve during the point of overlap. This is a critical time as it marks the beginning of the acceleration that draws the new charge into the cylinder.

Mike:
Yes it is true that a sonic wave leaves the exhaust valve when it opens but when it first leaves the valve it is a posative pressure wave, it then travels down the lenght of the tube until it gets to the end of the tube and enters the collector. Once the posative wave exits the primary tube the hot gases expand and creates a returning pressure wave of negative pressure.
Here is where it seems that everyone has gotten confused.
The negative pressure return wave hits the back of the EXHAUST valve(not intake) and creates a vac effect in the cylinder to evacuate the last remaining burnt exhaust gases. Heres where the tuned lenght part comes in. The primary tube lenght needs to be such as to time the arrival of the negative pressure wave at the exhaust valve at a timeframe that is very late in the exhaust blowdown of the exhaust cycle of the engine. That timeframe is important because at that moment the exhaust gas pressure is very low to nothing and there is still burnt gases present in the cylinder. The negative pressure or vac will suck much more of those burnt gases out of the cylinder thus leaving more room for a fresh air fuel charge and less dilution of that charge by burnt exhaust gases, that makes more power.
But this all needs to be timed correctly in order for it to be of any benefit, thus the need for properly sized(diameter) and lenght of primarie tube.
Should this first step in tuned pipe design be ignored and not followed then you might as well use stock manifolds because all you've built are tubular exhaust manifolds and not tuned pipes.
Here is an example of what I'm talking about. I ran the dimension #'s of the Kooks mid lenght headers to see just where they were actually tuned, it came out that they start to produce good scavenging at around 4000 RPM and peaked at right at 9000 RPM. That does'nt sound like they would be any better than stock manifolds does it? You have a good strong SC would you plop down 500-700 dollars for a set?

Dave:
I have been led to believe that this "suction" effect provides much better cylinder filling at the tuned rpm.

Mike:
I've already explained that the negative wave works at the exhaust valve so now you can see that this statement is incorrect, however I will expand on this.
The intake valve does infact have a pressure wave acting on it as well but it is 2 different waves we are talking about here and they have nothing to do with one another because each wave is from a different source. The wave that hits the back of the intake valve is a posative pressure wave that acts with a raming effect in order to ram the cylinder as full of fresh intake charge as it can. The sonic wave that acts on the intake valve is created by the shape and lenght of the intake port tract itself which is just like the tube diameter and lenght on the exhaust side only in reverse. These are 2 completely different events that are SEPERATED by the exhaust valve and intake valve and NOT one and the same. That appears to be where the confussion has set in.
The only time the exhaust wave would interact with the intake is during valve overlap, which by the way the stock SC cam does have overlap(time in which exhaust and intake valves are open at the same time) but it is minimal compared to NA cams. The reason boost cams have very little overlap is because you're using a blower or turbo to force the fresh intake charge into the cylinder rather than relying on the tuned intake port runner to ram the fresh charge into the cylinder. The intake manifold on my SVT is a good example of this intake tuning that I talk about here. That manifold has 2 port runners per cylinder(1 short and 1 long) and a butterfly valve just like a throttle plate installed in the short runner only. The computer is tuned so that when engine RPM is at 3750 the butterfly valve in the short runner is slamed wide open and thus the short runner takes over the flow of air. That short runner is of course tuned for higher RPM raming of the air charge than the long one, thus at RPM's from 3750 and up the short runner is more efficent and flows more air than the longer runner which keeps the power level up until 7000 RPM or so. I say or so because at 7000 RPM the rev limiter kicks in and she noses over. I think the port would still flow a good amount of air past 7000 RPM because the engine is still pulling hard until you hit the rev limiter. That engine because of its intake manifold design produces 2 torque peaks in its RPM range, one below 3750 and one above that. That is clear proof of sonic wave manipulation on the intake side of the engine.
That car almost mandates short shifting the tranny in racing situations because it revs so fast through the RPM range that by the time you think about shifting the gears you are bouncing all over the rev limiter. I'm somewhat amazed at how fast that motor revs, shifting really must be second nature to you without any thought because there's not enough time to think.

Dave:
I have also been led to believe (and common sense follows) that a supercharger or any charge pressurizing device negates the effect of this phenomenon on cylinder filling. It also stands to reason that if your cam does not have any valve overlap then this effect is mute.

Mike:
Hopefully after reading and understanding the explenations I have given you will see the flaw in this thinking.

Dave:
It also follows reason on a naturally aspirated application, that if you have a very large amount of overlap and header that is tuned too low you will actually draw the fresh charge right out the exhaust. I have understood that this is one reason that and exhaust system of sorts will often times help a race car run faster. Because the headers are actually drawing too much air and cheating the cylinder of a full charge.

Mike:
That is correct Dave and dead on, But here lyes the difference. With the SC we are raming air and fuel into the motor and thats why a boosted engine does not react well to large amounts of overlap. We've taken care of the intake side of the engine with a blower or turbo, but the exhaust side leaves alot to be desired. I'll try to further address that in my response to Randy because he's touch on some pertinant points to this which all ty into each other. :)
 
And now we can talk about step headers:O)

In the end I think we can expect two types of headers..Ones that work well on a mild modded motor/stock motor..Then ones for a more radical setup...

The reason I got rid of my Kooks shorties was because I knew though better then stock they were far from optimum..Thus the Kooks full lenghts now
 
Randy my friend you bring some good points and observations to the table, so lets talk.

Randy:
For cam over lap,or reversion of exhaust air can be somewhat takin care of
with proper built headers.

Mike:
You are correct Randy thats why designing and building tuned headers is more of an art form than a production process. The big header mfg'ers are more into production and sales than they are about producing a product with real world benefits, its all about the money baby!
Randy since you were a pro racer at one time I'm sure there was times that you were at the track with cars racing as well so you may know about a practice that I'm going to expose to everyone here that does not know about it.
The big header co's give contigincy(spelling) money to racers that advertise that they run there brand of headers, depending upon how they place in the race. A well known fact to all racers and the header mfg'ers is that the racers sporting the header mfg'ers stickers or metal name plates welded to there headers are NOT infact using there headers at all.
Truth is you could buy the metal name plates from Hooker headers from Summit or Jegs to mention a few places and weld them to your headers, if you placed well in those races where cont. money was given the header rep at the track would OK a check be cut to you as long as you have there sticker or nameplate.....am I the only one that this practice smells bad to?
All of that is done for the mfg'ers marketing boys and girls because they then inturn create an advertising blitz to promote sales by claiming so many good finish's at the race with there product. More like false advertising, but hey..they are displaying the co's decals on there car or the metal tag on the headers themselves so who knows otherwise.....right?

Randy:
As black as SC combustion chambers are ,I would say this may be a problem.

Mike:
You're onto something there Randy and all your experiance building and racing high perf motors has made you very observant, so consider this.
During my reply to Dave I talked about effectively scavenging the cylinders of burnt exhaust gases. Does it make sense to you that what you are observing with the blackened combustion chambers could also be caused by not effectively scavenging the cylinder of burnt gases as well?

Randy:
If you look at the floor of the exhaust port on a STEG head.
he does weld build up for the exhaust floors.To raise the radius for better flow.And he leaves the mouth floor of the exhaust header flange straight across the bottom.this is for reversion.

Mike:
You are correct Randy but there's more going on there than realized.
Stieg did not invent that port configuration, but let me be very clear about this. I am in no way trying to say or infer that Stieg is claiming to have invented that port, so please no flames.
That port was invented back in the early 80's by an a fella that I met and talk to from time to time named Larry Widmere. Those of you that do not know who Larry is he is the guy that built the heads for Bill Elliot when he set the speed record at Talladaga and pretty much dominated NASCAR. Another racer he helped was Bob Gliden when he owened NHRA Pro Stock. When Larry's support of these racers was pulled they withered away, he also built engines for Penske racing in the late 70's.
Anyway he designed that port as you mentioned Randy to seriously rework the short turn radius on Ford heads that proved to be a big holdback of power. One of the things that Larry accidentaly discovered by doing this was that the exhaust port now flowed at a supersonic speed. That inturn allowed the exhaust blowdown in the cylinder to happen very fast and much more efficently. The fact that the flat port floor caused a mismatch between the cylinder port and the exhaust header flange thus preventing reversion of the exhaust gases back into the cylinder was just a good side effect and not the intended reason for doing it.
By the way.....not to toot my own horn but I did that to my cylinder heads in late 99, I just never talked about it....speed secrets ya know! LOL!!!

Randy:
To make a header that works best all across the RPM range (daily driver).You will have to compromise.
Mike:
True dat is! But thats what makes designing headers fun, trying to come up with the best set of compromises for the big payoff.

Randy:
The best header is purpose built.One header for each job.

Mike:
True, but that applies to engines as well. Do we agree on that?

Randy:
If you build headers,I would want them to be coated with a heat barrier
and shiny.

Mike:
Well of course! LOL!!!!
I just noticed that I missed a few of Daves qeustions so the remainder of this post concerns those qeustions.

Dave:
Is that 1 5/8" primary pipe ID or OD?

Mike:
That would be OD Dave. All tubing is sized by OD where pipe on the other hand is sized by ID, that is the industry std.

Dave:
And where exactly do you find 2 3/8" pipe anyhow?

Mike:
Tubing Dave not pipe, that little slip of just 1 word when calling suppliers will get you the reply"Theres no such thing".
To be completely honest with you 2 3/8" tubing is not common but any big tubing supplier can get it for you if they do not stock it. :)
 
DamonSlowpokeBaumann said:
And now we can talk about step headers:O)

In the end I think we can expect two types of headers..Ones that work well on a mild modded motor/stock motor..Then ones for a more radical setup...

The reason I got rid of my Kooks shorties was because I knew though better then stock they were far from optimum..Thus the Kooks full lenghts now

Well Damon you may not believe this but step headers were experimented with as far back as the late 20's early 30's. They proved to be no help whatsoever except on engines that have siamesed exhaust ports(2 different cylinders exhaust valves flowing into 1 port). Like on Pontiac heads and I believe Flathead Fords, there may be others but those come to mind.
Today's engines that have responded to step headers usualy do so because the the stock manifolds and other avialable headers are designed so poorly to begin with.
You made a good move with your headers. :)
 
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