Header design

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(→Argument for larger collectors)
 
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==Introduction==
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To some, a header is just a bunch of tubes that connect the exhaust port to the rest of the exhaust system. To the more mechanically curious, it is a system of tuned length and diameter tubes connecting to a device which amplifies and optimizes the wavelength of the exhaust, effectively sucking burnt gases out of the engine's cylinders.
  
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In the street rod world, absolute mechanical efficiency often takes a back seat to appearance, clearance issues, and ease of installation. However, most of us overlook the benefits of a properly designed and built header and how it can improve drivability, power output and fuel economy. If you are building headers or modifying existing headers, why not try to keep the physical operation of a header in mind while working on it?
  
 
==Collector size==
 
==Collector size==
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The majority of torque "lost" from the bottom end of the power band has actually been moved upwards in the powerband, into the midrange. This can help performance during highway driving and towing, and may provide better passing power when needed. A more powerful midrange tends to make the low end seem less powerful, simply because the engine pulls better in a different part of the RPM range. Most people that think they lost low end power are simply noticing that the engine pulls better in a different way, even if NO low end power was ever lost.
 
The majority of torque "lost" from the bottom end of the power band has actually been moved upwards in the powerband, into the midrange. This can help performance during highway driving and towing, and may provide better passing power when needed. A more powerful midrange tends to make the low end seem less powerful, simply because the engine pulls better in a different part of the RPM range. Most people that think they lost low end power are simply noticing that the engine pulls better in a different way, even if NO low end power was ever lost.
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==Summary of header design principles==
 
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#A "shortie" or a "block hugger" header flows better than a stock manifold in most cases, and helps to produce more power than a stock manifold. However, it is not technically considered a header. They are easier to install than long tube headers in many cases, especially in late model vehicles, which makes them attractive.
 
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#Bigger diameter primary tubes are NOT better in most street applications.
 
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#The torque/power boost available from any header will occur over a specific RPM range. This is accentuated when using equal length headers; they tend to have a higher peak at the cost of average power/power under the curve, or the ''width'' of the powerband. Equal primary tube length is important for maximum power output, but not to the point of obsessing over it. A regular Tri-Y or 4 into 1 header will work better than the stock manifolds. Unequal length headers are a good compromise for a street driven vehicle in many cases; after all, engine design is a compromise.
 
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#A long and smooth collector with a moderate diameter will tend to favor the bottom end, conversely a short, large collector tends to favor the upper range.
 
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#Just like header tube size, be reasonable with the size of your exhaust system. Just do not undersize the system. If you're going to err, err on the larger side.
 
  
 
==180 degree exhaust system==
 
==180 degree exhaust system==
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The 1963 Ford Indy engine had the "bundle of snakes" exhaust system on the top with pipes crossing over to have 4 equally spaced exhaust charges in each exhaust header, some race car headers had pipes crossing under the trans to get equal charging in each header. This system is called a 180 degree exhaust. It has some advantages in racing situations, but for the most part it's a very difficult and costly system to manufacture, package and install/service in a production vehicle.
 
The 1963 Ford Indy engine had the "bundle of snakes" exhaust system on the top with pipes crossing over to have 4 equally spaced exhaust charges in each exhaust header, some race car headers had pipes crossing under the trans to get equal charging in each header. This system is called a 180 degree exhaust. It has some advantages in racing situations, but for the most part it's a very difficult and costly system to manufacture, package and install/service in a production vehicle.
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==Gaskets==
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There are many different types and sizes of header gaskets on the market today. Composite are common, as is fiber types. The composite gaskets seem to hold up a little better, all else being equal, but the main thing is to retighten the header bolts often- like every time the engine is heat cycled- until the fasteners take a set.
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[[File:Foil exh gasket sbc1.jpg]]
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{{!}}Remember- keeping the bolts tight is very important to keeping the gaskets from burning out.
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For the SBC and any other engine that uses these gaskets as a stock replacement: If/when the gaskets take a dump, try a set of the foil backed composite gaskets that come in most rebuild gasket sets. If they'll fit the head and header ports, they will work as good as most any more expensive composite gasket if the bolts are kept tight.
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Regardless of what gasket that is used, trim the ID to fit the largest port, be it the header or the head port so there's no overhang into the port. After trimming, start all the bolts and just drop the gaskets into place. Other header gaskets can have the bolt holes slotted in the same way as the foil backed gaskets shown above, for easier installation.
  
 
==See also==
 
==See also==
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[http://en.wikipedia.org/wiki/Manifold_%28automotive_engineering%29 Wikipedia article on exhaust manifolds]
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*Wikipedia article on [http://en.wikipedia.org/wiki/Manifold_%28automotive_engineering%29 exhaust manifolds]
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*[[Headers]]
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* http://www.wallaceracing.com/header_length.php
  
 
[[Category:Engine]]
 
[[Category:Engine]]
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[[Category:Exhaust]]
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[[Category:Undeveloped articles]]
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[[Category:Undeveloped Engine articles]]
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[[Category:Undeveloped Exhaust articles]]

Latest revision as of 14:46, 5 May 2022

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