Short vs Long Tube Headers - Team Camaro Tech
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post #1 of 21 (permalink) Old Apr 29th, 15, 07:43 PM Thread Starter
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Short vs Long Tube Headers

What is the big difference, other than the obvious difference in long vs short tube headers as far as performance is concerned?

Prepare to be the center of attention when you drive a first generation Camaro. You will be gawked at. Grown men & women will coo like children when you drive past. Children will scream like babies. Dogs & cats will get along. Does it get any better?
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post #2 of 21 (permalink) Old Apr 29th, 15, 08:18 PM
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Re: Short vs Long Tube Headers

Both are better than stock manifolds, I think it is just how much you need your engine to breath.
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post #3 of 21 (permalink) Old Apr 29th, 15, 08:19 PM
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Re: Short vs Long Tube Headers

shorter tubes = higher rpm HP.. and long tubes (more lower rpm torque)...

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post #4 of 21 (permalink) Old Apr 29th, 15, 09:10 PM Thread Starter
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Re: Short vs Long Tube Headers

Quote:
Originally Posted by 69Z28-RS View Post
shorter tubes = higher rpm HP.. and long tubes (more lower rpm torque)...

Thanks guys, these are the answers I was looking for.

Prepare to be the center of attention when you drive a first generation Camaro. You will be gawked at. Grown men & women will coo like children when you drive past. Children will scream like babies. Dogs & cats will get along. Does it get any better?
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post #5 of 21 (permalink) Old Apr 29th, 15, 09:45 PM
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Re: Short vs Long Tube Headers

Diameter of the primary tubes and length can make a significant difference as well.

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post #6 of 21 (permalink) Old Apr 30th, 15, 02:03 AM
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Re: Short vs Long Tube Headers

If you are cruising the street with a SBC then headers are highly over rated. The two and a half inch ID stock Ram's Horn design cast iron manifold can flow as much exhaust gas at small tube header can up to 4,600 RPM. A cast iron manifold may not look very cool under the hood but they also don't leak.

So why the desire for tubular headers. Two fold: First and foremost is everyone wants to be part of the crowd, so they gotta have what everyone else has. Face it most have no idea as to the fluid dynamics involved with exhaust flow engineering. I can crag out my old college text books and talk about wave theory and the rest, but basically everyone today has headers because everyone started copying their hero's race car wanting to be just like him.

Long, equal length, big primary tubes with adjustable collector length headers were what people like Hooker, Stahl, Headman, and the others were selling back when these cars were new. But then again back then the only people that lowered their cars where looked down upon as being ignorant immigrants from south of the border. A race car never then or now was designed to run on the street, so they were uncapped all the time and loud. Today we run little to anything in the way of mufflers and install exhaust pipes so big they would work on a diesel truck. But then again glass packs were popular even back in the fifties before they became an over the counter item that you had to make yourself in your garage with an acetylene torch and a coat hanger out of the closet.

Shorty headers are today popular because of fitment issues, as well as reduced cost. Though today it costs more to buy headers than it does to make your own; which is what most of the guys who are now selling headers in a box welded by robots used to do in their muffler shops. Long tube headers are no longer equal length, or even attempt to fool anyone into thinking they are equal length. That went out the window when header manufactures stop being a one man garage operation and became a big business with investment bankers managing the company.

I mentioned uncapped above because that is very important as far as the word tuned length is concerned. Without an uncapped header you get no standing waves in the tubes and as such no scavenging. So that can be ignored. The second reason you want a header and the reason they do give a boost to a stone stock engine of close to twenty horsepower is because the two adjacent cylinders in the firing order are segregated to prevent the closing valve cylinder to be polluted by waste gasses from the opening valve cylinder next to it. With a header pipe with a nine inch long tubes the cylinders are isolated from each other so that there is no contamination of the incoming charge.

That's it. There is no other reason to swap out stock exhaust for tubular headers except if you intend to spend most of your drive time running in excess of 4600 RPM or to separate the two cylinders five and seven. Oh except for the fact that you just gotta have them, because every one else has them. Or your SBC cast iron exhaust manifold is a log type as found on newer cars and big block Chevys (which have a really poor designed exhaust port in the stock head that can use all the help it can get) then it is a no brainer to go with headers.

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post #7 of 21 (permalink) Old Apr 30th, 15, 04:58 AM
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Re: Short vs Long Tube Headers

here is an interesting read from sanderson headers
Sanderson Headers :: Let's Get Technical

Let's Get Technical

Let's Get Technical
Sanderson Header Tech"Even if you're running a radical cam and a blower, you're better off sizing your headers smaller ... unless you do most of your driving at full throttle."

It's no secret that a good set of headers is one of your best performance investments. In fact, most engine builders say that headers are one of the first things you should change to when modifying your motor. But before you plunk down your cash, remember that a couple factors determine what's going to work best for your particular application.

The first thing to consider is the intended use of your vehicle. Are you building a daily driver, a sometimes bracket racer, or a dedicated quarter-miler? The RPM range where you want the most torque, along with the displacement (size) of the engine plus any other serious modifications and power-adders (camshaft, blower/supercharger, cylinder heads, nitrous, etc.) are equally important factors.

Stock manifolds are mass produced and are designed to clear all the accessories offered for any vehicle the engine block may go into. So naturally, performance is compromised by manufacturing requirements. Tubular headers are built for power and their design can be very specific.

Let's look at how headers work, and clear up a couple common misconceptions. First is the size of the primary tube. It's easy to assume the bigger the tube the better, but that's not the case.

The fact is, primary tubes that are too large actually cost you torque and horsepower by slowing down the rate at which the exhaust gases travel through the system. Think of your engine as an air pump. Every time the exhaust leaves the combustion chamber it is being forced into the primary tube for that cylinder.

Horsepower and Torque as a function of header tube diameter

Smaller diameter pipes flow less volume than larger ones, but the exhaust in the smaller pipe flows faster. Until you reach the RPM where the sheer volume of exhaust gases require bigger primary tube diameters, smaller tubes will scavenge the cylinders more efficiently. If you're using the engine in the 1,500 to 3,500 RPM range, which is typical for a street-driven vehicle, you definitely want 1-1/2" to 1-5/8" primary tubes for any small block and 1-3/4" to 1-7/8" for a big block engine. Any bigger and you'll lose a considerable amount of low end torque. beyond 3,500 RPM it is a question of where you want the power peaks. As you can see from the charts on this page, small tube headers do not lose their edge in horsepower and torque until you exceed 5,500 RPM.

Even if you're running a radical camshaft and blower, you're better off sizing your headers smaller rather than larger, unless you plan to do most of your driving at full throttle. The headers we build are sized correctly for even the most heavily modified street motors.


--------------------------------------------------------------------------------

The second biggest controversy in header design is the "equal length" versus "shorty" styles - which is best? Like most performance products, there are advantages and disadvantages to both.

Exhaust headers with equal length tubes have been shown to develop slightly more power on an open exhaust system, but not when hooked up to a street system with mufflers. Fact is, most street motors with shorty headers will produce the same power as they would with expensive equal length headers.

Equal length tubes can produce more power, but they have to be the right length for the specific motor at the RPM range where you want the power. What that means is lots of custom fabrication and dyno testing, which translates into lots of time and money.

For racing applications, the slight gain may justify the cost, but competition cars can be more easily built "around the engine" than street cars. When you're working within the confines of a given body style and chassis, with motor mounts, starter, steering linkage and accessories to think about, the way the headers fit become more important.

That's where the compact or "shorty" style header shines. You get a significant performance increase compared to stock exhaust manifolds, at an off-the-shelf price. Plus, Sanderson headers provide excellent clearance around spark plugs, starter and chassis components, as well as ground clearance for lowered vehicles. The charts on this page illustrate just how little power you trade off for the much lower cost and easy installation of compact headers.
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post #8 of 21 (permalink) Old Apr 30th, 15, 07:51 AM
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Re: Short vs Long Tube Headers

Rodney Davis from headerdesign.com wrote this description of the difference:

An independence header design tries to make full use of the blowdown wave energy to scavenge the cylinder before and during overlap. The header is designed to work from the midrange on up. A blowdown wave might peak at 2.5Atmospheres in the exhaust port, and propagates down the primary header pipe through the exhaust gas in the pipe. It is reflected at the expansion into the collector as a suction wave, which propagates back up the header pipe to the exhaust port. Suction wave strength might be 0.5atmospheres or so. The primary diameter goes with engine power, and determines wave strength. The primary length goes with time, and determines RPM range for effective scavenging by the first reflected suction wave. The collector diameter and length determine the width, strength, and shape of the reflected suction wave. Multiple primaries can use a common collector with little cylinder-to-cylinder interference, especially when an x or y-pipe is used for V8's.

An interference header design tries to cancel waves in the pipes, leaving just a pressure gradient in the exhaust system to move gas down the pipes. This provides very predictable engine performance at lower speeds, and doesn't draw charge out the exhaust during overlap at higher speeds. The blowdown wave peak pressure is truncated because of early expansion into a secondary pipe and coupled primary from an adjacent cylinder. Blowdown wave is divided and travels up the coupled primary where it is reflected off the closed exhaust valve as a compression wave. The blowdown wave also travels down the secondary pipe to a tertiary pipe. Expansion into the tertiary pipe causes a reflected suction wave. The reflected compression wave and suction wave will arrive back at the exhaust port in question at the same time in a true interference design. By altering the primary and secondary lengths, you can make an independence/interference hybrid header for various applications. I don't do this type of design.

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post #9 of 21 (permalink) Old Apr 30th, 15, 08:47 AM
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Re: Short vs Long Tube Headers

So...

Quote:
Originally Posted by bigblockragtop View Post
Both are better than stock manifolds, I think it is just how much you need your engine to breath.
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post #10 of 21 (permalink) Old Apr 30th, 15, 08:37 PM Thread Starter
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Re: Short vs Long Tube Headers

I'm with you on the leaks. I don't think there is a header made that don't blow gaskets, even if you do cut the flange plate I just had 2.5 with Flowmaster 40's put on the 69. Sounds great.

Quote:
Originally Posted by Larger Dave View Post
If you are cruising the street with a SBC then headers are highly over rated. The two and a half inch ID stock Ram's Horn design cast iron manifold can flow as much exhaust gas at small tube header can up to 4,600 RPM. A cast iron manifold may not look very cool under the hood but they also don't leak.

So why the desire for tubular headers. Two fold: First and foremost is everyone wants to be part of the crowd, so they gotta have what everyone else has. Face it most have no idea as to the fluid dynamics involved with exhaust flow engineering. I can crag out my old college text books and talk about wave theory and the rest, but basically everyone today has headers because everyone started copying their hero's race car wanting to be just like him.

Long, equal length, big primary tubes with adjustable collector length headers were what people like Hooker, Stahl, Headman, and the others were selling back when these cars were new. But then again back then the only people that lowered their cars where looked down upon as being ignorant immigrants from south of the border. A race car never then or now was designed to run on the street, so they were uncapped all the time and loud. Today we run little to anything in the way of mufflers and install exhaust pipes so big they would work on a diesel truck. But then again glass packs were popular even back in the fifties before they became an over the counter item that you had to make yourself in your garage with an acetylene torch and a coat hanger out of the closet.

Shorty headers are today popular because of fitment issues, as well as reduced cost. Though today it costs more to buy headers than it does to make your own; which is what most of the guys who are now selling headers in a box welded by robots used to do in their muffler shops. Long tube headers are no longer equal length, or even attempt to fool anyone into thinking they are equal length. That went out the window when header manufactures stop being a one man garage operation and became a big business with investment bankers managing the company.

I mentioned uncapped above because that is very important as far as the word tuned length is concerned. Without an uncapped header you get no standing waves in the tubes and as such no scavenging. So that can be ignored. The second reason you want a header and the reason they do give a boost to a stone stock engine of close to twenty horsepower is because the two adjacent cylinders in the firing order are segregated to prevent the closing valve cylinder to be polluted by waste gasses from the opening valve cylinder next to it. With a header pipe with a nine inch long tubes the cylinders are isolated from each other so that there is no contamination of the incoming charge.

That's it. There is no other reason to swap out stock exhaust for tubular headers except if you intend to spend most of your drive time running in excess of 4600 RPM or to separate the two cylinders five and seven. Oh except for the fact that you just gotta have them, because every one else has them. Or your SBC cast iron exhaust manifold is a log type as found on newer cars and big block Chevys (which have a really poor designed exhaust port in the stock head that can use all the help it can get) then it is a no brainer to go with headers.

Big Dave

Prepare to be the center of attention when you drive a first generation Camaro. You will be gawked at. Grown men & women will coo like children when you drive past. Children will scream like babies. Dogs & cats will get along. Does it get any better?
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post #11 of 21 (permalink) Old Apr 30th, 15, 08:55 PM Thread Starter
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Re: Short vs Long Tube Headers

Kinda, actually it is unrelated but back in the 80's I used to drag race a 750 Kawasaki 2 stroke with Wirges expansion (stinger) chambers on it. The motorcycle got knocked off the stand by someone backing a trailer and it bent two of the chambers on one side, sorta bent the stingers in the up position about 5-10 degrees. I left them alone how ever, it shaved close to 2/10's of a second off my 1/4 mile et.....and this was time after time. I never attempted to do anything with them and at a race in Commerce, GA, Wirges had a vendor trailer there and I told them what had happened.....the were shocked and passed the info on to their tech dept. I have no idea if they done anything with it as I went boat racing shortly after.

Guess I should have bought the trailer backer dinner as he caused me to win several races that I wouldn't have won otherwise.

Prepare to be the center of attention when you drive a first generation Camaro. You will be gawked at. Grown men & women will coo like children when you drive past. Children will scream like babies. Dogs & cats will get along. Does it get any better?
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post #12 of 21 (permalink) Old May 1st, 15, 05:52 AM
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Re: Short vs Long Tube Headers

Quote:
Originally Posted by SS68 View Post
Kinda, actually it is unrelated but back in the 80's I used to drag race a 750 Kawasaki 2 stroke with Wirges expansion (stinger) chambers on it. The motorcycle got knocked off the stand by someone backing a trailer and it bent two of the chambers on one side, sorta bent the stingers in the up position about 5-10 degrees. I left them alone how ever, it shaved close to 2/10's of a second off my 1/4 mile et.....and this was time after time. I never attempted to do anything with them and at a race in Commerce, GA, Wirges had a vendor trailer there and I told them what had happened.....the were shocked and passed the info on to their tech dept. I have no idea if they done anything with it as I went boat racing shortly after.

Guess I should have bought the trailer backer dinner as he caused me to win several races that I wouldn't have won otherwise.
This is because a two stroke engine and diesel engines are very intolerant of any back pressure in the exhaust (needs to be as close to atmospheric as possible).

The Otto cycle because almost all of the useable energy is extracted in very few crank shaft rotational degrees from TDC dumps out it's exhaust at a much higher pressure (high enough that work can be extracted with a turbo charger to drive further compression of the input charge).

This is why a German engineer added an expansion chamber to the Welsh Engineers improvement of the Scottish engineer's original cross port two stroke design back in 1911 that the Japanese manufacturers all copied after WWII to sell cheap Jap two stroke bikes (the Honda was a four stroke from the beginning) in the US in the sixties starting with the Yamahas in 1948. The megaphone-reversed funnel expansion chamber acts like an echo chamber reflecting the exhaust pulse (not a sound wave) back into the exhaust port to scavenge the spent charge out of the cylinder as a fresh charge is forced into the chamber by the descending piston.

The best two cycle engine isn't found on a Yamaha or Kawasaki but in a 1966 SAAB three cylinder 850 cc that used everything know up to that point in time; including the Swedish engineer's contributing idea of redirecting the input charge to flow across the roof of the combustion chamber rather than flow out the exhaust port, for more gas (and oil) inside the chamber to burn making more power. The reason we don't use two cycle engines is their limited power range (RPM band where they make power) and the fact that they all burn oil which is emission unfriendly.

Your dent tuned the exhaust pulse to augment the breathing capabilities of your engine. I doubt without todays current CNC machines reading the surface area to determine the exact volume in the expansion chamber that it could be reproduced. It would be intriguing to model the wave forms to find out what was going on in side though if you still have it.

Big Dave
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post #13 of 21 (permalink) Old May 1st, 15, 08:34 AM
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Re: Short vs Long Tube Headers

For the guys saying all headers leak, I don't know what headers or gaskets you guys have been using but I haven't had leak or blowout issues since my early twenties using crappy used headers and paper gaskets. Don't use paper gaskets, or cheap headers with poor flanges, or it will leak.

The short answer about headers, it depends. On a street car with a cheap mass produced header, the difference between the two isn't much. Power peaks will move around.
On a well designed header on a motor that makes some power, it can be a big difference. That's why a custom set of headers costs more than a mass produced header.
Some guys don't care about leaving power on the table even if they are not using it all of the time, some guys do.

We dropped a 406 that ran low 11's in one car into another to race a weekend event, but the headers wouldn't fit so we used hogged out large Rams horn manifolds that were laying around, the car just cracked the 12's. There was a weight difference but only 2-3 tenths worth probably.

Sean

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post #14 of 21 (permalink) Old May 1st, 15, 09:05 AM
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Re: Short vs Long Tube Headers

Wonder what the op is running anyway.
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post #15 of 21 (permalink) Old May 1st, 15, 11:34 PM Thread Starter
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Re: Short vs Long Tube Headers

Thats easy, RAMS HORNS !! 2.5" all the way back, with an H pipe and Flowmaster 40's.

Quote:
Originally Posted by bigblockragtop View Post
Wonder what the op is running anyway.

Prepare to be the center of attention when you drive a first generation Camaro. You will be gawked at. Grown men & women will coo like children when you drive past. Children will scream like babies. Dogs & cats will get along. Does it get any better?
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