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Old 07-14-2017, 05:48 PM   #1
nad427

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Default An interesting header test.

Didn't know quite where to put this, so feel free to move it if need be.

This is 4 yrs old, but it's still eye opening info. What really got me was the coating vs non-coating temp difference. That's going to mean a bunch to some here. https://www.youtube.com/watch?v=O1bXPNy1Yn4

Also the tube size HP loss and gain is going to confuse some. The expert-speak always has always said something contrary to that.

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Old 07-14-2017, 08:47 PM   #2
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Folks don't realize how important headers can be just to get those few extra HP
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Old 07-14-2017, 08:58 PM   #3
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the thing to keep in mind here is that this is a 427 not a 454,502,540. etc. the bigger the engine the bigger the tube to a point. those 1 7/8 headers will be awesome on a 427 SBC
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Old 07-14-2017, 09:29 PM   #4
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Header size is directly related to the power potential. I.e., it doesn't matter if it's a 283, a 350, a 427, or a 502 - if you potentially have a 600 hp engine, then there's a certain tube size that works to support that. Looks like it's 1-7/8" tubes for 600 hp - and I'll agree with that.

Their point about collector extensions is probably valid on a streetable engine, particularly if you race it below the torque peak. Above the torque peak, not so much, as their results showed.

What they didn't show, I assume because few will go to the trouble and expense - is that stepped headers with the correct beginning tube size make some nice gains (30-40 hp) based on my experience. I also found that one step, two steps, etc. don't make much difference as long as you have a step.

Equal lengths are also overrated unless the unequal differences are huge.
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Old 07-15-2017, 06:33 PM   #5
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Quote:
Originally Posted by Rick_L View Post
What they didn't show, I assume because few will go to the trouble and expense - is that stepped headers with the correct beginning tube size make some nice gains (30-40 hp) based on my experience. I also found that one step, two steps, etc. don't make much difference as long as you have a step.
I'm in a quandary over that. I've never had any stepped headers, nor have I ever experimented with them. I don't have any equipment to do so either (dyno).

What I don't understand is that common sense tells me that a larger beginning tube, then a smaller tube as the gasses cool and condense some as they get further down the headers would benefit the flow more rather than the smaller diameter first.

The stepped headers I've seen start out with the smaller tube first, then go larger. Maybe I'm looking at this backwards somehow.

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Old 07-15-2017, 06:43 PM   #6
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Yes they start out small and get bigger. I don't know how to clearly explain their advantage, nor why it's so dramatic. I just know that it works very well.

A typical stepped header starts out with the same tube size that works best if you had one tube size. I.e., if a 1-7/8" header worked better than a 2" header on a given engine, then your stepped header would start out at 1-7/8".

I also want to clarify my 30-40 hp statement. That would be the typical maximum gain at one rpm. Average gain would be a bit less.

I don't know why you don't see stepped headers advertised more. All but a few are custom made.
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Old 07-16-2017, 10:25 PM   #7
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HA good information. Ill put it to use when I finish my tire shredding 235

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