Editing Header design

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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.

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?

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==Summary of header design principles==
#A "shortie" or a "block hugger" flows better than a stock manifold, and helps to produce more power than stock. However, it is not technically considered a header. They are easier to install in a stock style exhaust system, which makes them attractive.
#Bigger diameter primary tubes are NOT better in most street applications.
#The torque/power boost available from a header will occur at a specific RPM that can be easily determined.  The price paid for this boost is likely lower power at other RPMs.  All engine design is compromise.
#Equal primary tube length is very important for tuning and power output, but not to the point of obsessing over it. A regular Tri Y or 4-1 header will work wonders over the stock manifolds.
#A long and smooth collector is a good thing.
#Just like header tube size, be reasonable with the size of your exhaust system.
One thing that has not been discussed is the unequal firing order from one bank to the other.  I did an research paper  on Exhaust tuning when I was in college, A Jaguar racing engine had %105 volumetric efficiency,,, the torque peaks vs rpm  looked like the grand teton mountains   Start with a sheet of graph paper and draw the engine in plan view then draw a line 8 blocks long from cylinder no 1 . a line 7 blocks from cylinder firing next.... 6 blocks from the cylinder that fired third   etc  and so on following the firing order. .   You will see the lines are not uniformly distributed ,  the ford 63 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

==See also==
[http://en.wikipedia.org/wiki/Manifold_%28automotive_engineering%29 Wikipedia article on exhaust manifolds]

[[Category:Engine]]
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