Header design
m (Reverted edit of 199.184.119.113, changed back to last version by Jon) |
m (expanded equal length discussion) |
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the driver's side rear tube (in yellow) must be about 10"-12" shorter than the next tube (in red). | the driver's side rear tube (in yellow) must be about 10"-12" shorter than the next tube (in red). | ||
| − | This would mean that the | + | This would mean that the short primary tube would scavenge at a higher RPM and the long primary tube would scavenge at a lower RPM for the respecive cylinder. Therefore the clyinder with the short tube will be running lean at low RPM and the long tube clyinder will be running lean at the high RPM and would require different jetting and timing than the others as well. How do you do that with a standard kettering distrubutor and a simple carburetor?. Thats why equal length is important, so you can tune your car. |
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| + | This has been demonstrated on a '69 corvette with Headman side exhaust. The engine did not respond to idle screw adjustments at all. There was an 18" difference in primary tube lengths. Switching to an equal length header made adjusting the carb easy and idle vacuum went up 2 inches of vacuum. | ||
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| + | Equalness is usually defined as being within 2 inches between the lonest tube and the shortest, about as close as you can measure with a tape measure at the swap meet. | ||
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| + | There have been claims by some manufacturers that unequal lengths broaden the torque curve do to different clyinders performing better at different RPM. It is left to the reader to decide if the flattening to torque curve is a good thing to be doing with headers. | ||
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I guess all we can do is create our headers properly or reconfigure existing units to work as they should and not give ourselves tuning headaches. When big name header manufacturers say equal length, they must be talking out their collectors. | I guess all we can do is create our headers properly or reconfigure existing units to work as they should and not give ourselves tuning headaches. When big name header manufacturers say equal length, they must be talking out their collectors. | ||
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