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Thread: Header design/build good read

  1. #1

    Default Header design/build good read

    Have been doing research on building my own headers and stumbled across this site. Some very interesting ideas and test results, especially in the "Header design comments" page, worth the read.
    http://www.headersbyed.com/index.htm

  2. #2

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    Quote Originally Posted by TurboJoe62 View Post
    Have been doing research on building my own headers and stumbled across this site. Some very interesting ideas and test results, especially in the "Header design comments" page, worth the read.
    http://www.headersbyed.com/index.htm
    Funny this is being brought up when not two days ago I was thinking of the guy who built the best set of headers for his 67 Nova. These headers had no collector. They exited at the bottom of the car at different lengths with the tubes tack welded to each other. The car was strictly a track car. The only reason we put collectors on is to be able to bolt up exhaust pipes as the collector creates a platform for flanges. Now why were these equal length headers better than equal length headers from manufacturers? Because in order to create the collector flange and keep tubes equal length, headers had to be bent at their beginnings of the header tube run and had to go through all kinds of contortions to not only create the equal length but to also fit within the engine compartment.. These bends and contortions were not the best for efficient exhaust flow. This guy solved all that by creating equal length tubes and didn't have to worry about making them all equal to put a collector flange on.

    Years back (perhaps Mickey Thompson?) a company built headers with this concept and in order to make them marketable for street use, the collectors were very long to accommodate the header tubes which came out all different lengths within the collector itself. Many didn't realize how good these headers were and eventually, this company folded its header enterprise. The reason? People didn't like the look under the hood as the headers were quite nondescript simply exiting straight down from the engine. They associated the contorted bends necessary for equal length tubes everyone else used, as a "performance " look much like people associate the sound of cam overlap with.

  3. #3



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    I've seen that page and thought about trying his tapered collector extensions as I'm not running mufflers from now on because header Evac.
    In one of David Vizard's book, "How to Build PAH", he says equal length primaries are not as important as the secondaries.
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  4. #4

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    Quote Originally Posted by Adobedude View Post
    I've seen that page and thought about trying his tapered collector extensions as I'm not running mufflers from now on because header Evac.
    In one of David Vizard's book, "How to Build PAH", he says equal length primaries are not as important as the secondaries.
    Found this to be true on the factory (and mine) Cobra Jets in 1968. Primary diameter seems to be more important but the largest differences occurred when we played around with collector length. Most full length headers use this short, little stub of a collector maybe 4 or 5" in length which is fine for the street. If you have a race car that lives in the upper echelon of rpms, this is a big mistake. We installed headers with 12" collectors and picked up 2 to 3 tenths. We tried all kinds of lengths with some as long as 18" but for our rpm range which was 6000 and over,
    12" seemed to be the sweet spot.
    Now if memory serves, the diameter of the secondary was also important. I think the diameter ratio was 1.8 times the primary width. So with 2" primaries, you have 3.6" wide collectors. As you can't find 3.6" pipe diameter, drop down to the nearest one which would be 3.5" pipe. These collector extensions are shit easy to make.

  5. #5

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    Quote Originally Posted by Adobedude View Post
    I've seen that page and thought about trying his tapered collector extensions as I'm not running mufflers from now on because header Evac.
    In one of David Vizard's book, "How to Build PAH", he says equal length primaries are not as important as the secondaries.
    Be very curious to see your results using different collector extensions and designs. Have seen what David Vizard says regarding that prove out correct across many knowledgeable tests. I was a little surprised that Ed said changing size/shape of collector extension has nearly the same effect as changing collector sizing. I kinda thought that being further downstream would not produce as much change as he has found. I knew changing length has a substantial change.

  6. #6

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    Quote Originally Posted by arro222 View Post
    Found this to be true on the factory (and mine) Cobra Jets in 1968. Primary diameter seems to be more important but the largest differences occurred when we played around with collector length. Most full length headers use this short, little stub of a collector maybe 4 or 5" in length which is fine for the street. If you have a race car that lives in the upper echelon of rpms, this is a big mistake. We installed headers with 12" collectors and picked up 2 to 3 tenths. We tried all kinds of lengths with some as long as 18" but for our rpm range which was 6000 and over,
    12" seemed to be the sweet spot.
    Now if memory serves, the diameter of the secondary was also important. I think the diameter ratio was 1.8 times the primary width. So with 2" primaries, you have 3.6" wide collectors. As you can't find 3.6" pipe diameter, drop down to the nearest one which would be 3.5" pipe. These collector extensions are shit easy to make.
    Kinda cool that some old ideas were soooo spot on I have seen the old time method of painting header extension and then cutting it to length where the paint stops burning still prove out in a few modern engine builds!
    My research (reading, not personal) has found that 1.6-1.7 times primary = street, 1.7-1.8 = street/strip and 1.8-2 = race and also as you said if comes out unavailable to go next size down, never up.

  7. #7
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    tuning headers is just as important and same theory as tuning intake manifold. Lots o science in there.

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