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Which one of these exhaust headers is better?

Which one of these exhaust headers is better?

Old 05-18-2016, 08:54 PM
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Default Which one of these exhaust headers is better?

I was browsing the "vintage" parts section at my LHS and I came across these exhaust headers from HPI:



I'd seen them before but never paid much attention to them. However, this time I noticed two potential advantages vs. the mandrel-bent-tube headers that are commonplace nowadays:

1) The header is the full width of the exhaust port the whole way down, whereas mandrel-bent-tube headers have to taper down to the width of the tube (and sometimes there's no taper at all unless you add one yourself with a Dremel);
2) The header terminates in a swirl chamber (see below);



The swirl chamber is there to reduce turbulence in what would otherwise be a sharp change of direction for the exhaust gases, but I don't know if it has any benefits besides that. The full-width header might be beneficial, but then it still has to taper down at the end, in order to connect to the exhaust pipe, so maybe there's no net gain, I dunno. It was only 5 bucks, so it's not a big deal if it turns out to be junk, but I'm curious if there are any applications where this style of header is superior. Anyone know from experience?

Last edited by fyrstormer; 03-29-2018 at 04:38 PM.
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Old 05-18-2016, 11:17 PM
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The cast manifold is less conducive to efficient pressure wave action. They are cheaper to make though, in an attempt at keeping production costs down on the RTR cars they came on over a long period of production. Try them back to back if you feel like experimenting, then port match the tubular manifold and try it again.
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Old 05-19-2016, 12:05 AM
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I already port-matched the tubular header. Not sure I could tell any difference before and after, but I know it must be better.

I see what you mean about the pressure waves not propagating back through the cast header very well. A mandrel-bent tube would be better for that. Supposing I'm not running a tuned pipe though, would the pressure-wave problem still exist?
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Old 05-19-2016, 04:47 AM
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If you're not running a tuned pipe the header issue becomes a non-issue as it's going to be like running a can muffler. No expansion chamber-cylinder pressurizing effect... I don't see why anyone would do that though.
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Old 05-19-2016, 08:18 AM
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The cast one also makes it harder for the exhaust to go out it hits a 90 degree and then it has to find its way out(and back), whereas the pipe one has a much smoother path to the pipe.
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Old 05-19-2016, 01:47 PM
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Originally Posted by FirebladeRX7 View Post
If you're not running a tuned pipe the header issue becomes a non-issue as it's going to be like running a can muffler. No expansion chamber-cylinder pressurizing effect... I don't see why anyone would do that though.
Better low-end torque, smoother powerband, and less screaming at high RPM. I.e. better for bashing, where the engine isn't being kept in a narrow range of high RPMs constantly for the sake of maximum performance.
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