Header primary pipe sequence into collector for 4/7 swap

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redliner
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Header primary pipe sequence into collector for 4/7 swap

Post by redliner » Wed Oct 04, 2017 10:18 am

Hey guys I am getting ready to build a new set of headers. I have a sbc with a 4/7 swap in the firing order and I would like to place the primary tubes in the collector in the order which helps evacuate the cylinders the most effectively. Am I over thinking this or..... I have the pipemax program which has told me the diameter and length needed but I wondered about placing them in the collector in a certain order... These fenderwell headers for my 42 Stude coupe will be 2 " for about 10 " then 2- 1/8" for about 20" finishing with a 16" 3- 5/8" collector.

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Re: Header primary pipe sequence into collector for 4/7 swap

Post by DaveMcLain » Wed Oct 04, 2017 10:21 am

How could this make any difference what so ever?

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Re: Header primary pipe sequence into collector for 4/7 swap

Post by redliner » Wed Oct 04, 2017 10:43 am

DaveMcLain wrote:
Wed Oct 04, 2017 10:21 am
How could this make any difference what so ever?
The exhaust leaving the primary tubes create a pulse that helps suck the incoming mixture into the cylinder instead of relying on atmospheric pressure.I am just a self taught shade tree mechanic at best but this is how I understand it.... perhaps someone else can explain it better...

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Re: Header primary pipe sequence into collector for 4/7 swap

Post by DaveMcLain » Wed Oct 04, 2017 11:35 am

redliner wrote:
Wed Oct 04, 2017 10:43 am
DaveMcLain wrote:
Wed Oct 04, 2017 10:21 am
How could this make any difference what so ever?
The exhaust leaving the primary tubes create a pulse that helps suck the incoming mixture into the cylinder instead of relying on atmospheric pressure.I am just a self taught shade tree mechanic at best but this is how I understand it.... perhaps someone else can explain it better...
When the positive pressure wave from the primary tube enters the collector it collapses and it then sends a negative pressure wave back up that primary pipe. The partially collapsed positive wave continues to the end of the collector where it collapses again and this time the negative wave influences all of the primary pipes. This is why having a collector is usually better than individual pipes because you have more negative pulses. But in what position the primary pipes enter the collector how can that make any difference?

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Re: Header primary pipe sequence into collector for 4/7 swap

Post by redliner » Wed Oct 04, 2017 11:40 am

DaveMcLain wrote:
Wed Oct 04, 2017 11:35 am
redliner wrote:
Wed Oct 04, 2017 10:43 am
DaveMcLain wrote:
Wed Oct 04, 2017 10:21 am
How could this make any difference what so ever?
The exhaust leaving the primary tubes create a pulse that helps suck the incoming mixture into the cylinder instead of relying on atmospheric pressure.I am just a self taught shade tree mechanic at best but this is how I understand it.... perhaps someone else can explain it better...
When the positive pressure wave from the primary tube enters the collector it collapses and it then sends a negative pressure wave back up that primary pipe. The partially collapsed positive wave continues to the end of the collector where it collapses again and this time the negative wave influences all of the primary pipes. This is why having a collector is usually better than individual pipes because you have more negative pulses. But in what position the primary pipes enter the collector how can that make any difference?
They dont is what I gather from your post. This is the info I am looking for. I do not know whether or not it makes a difference, your explanation seems legit.

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Re: Header primary pipe sequence into collector for 4/7 swap

Post by RevTheory » Wed Oct 04, 2017 12:04 pm

I've heard you want them to hit the collector clockwise but who knows...

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Re: Header primary pipe sequence into collector for 4/7 swap

Post by redliner » Wed Oct 04, 2017 12:14 pm

RevTheory wrote:
Wed Oct 04, 2017 12:04 pm
I've heard you want them to hit the collector clockwise but who knows...
Clockwise in the firing order I take it.....

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Re: Header primary pipe sequence into collector for 4/7 swap

Post by RevTheory » Wed Oct 04, 2017 12:21 pm

Whatever the sequence is, just hit the collector clockwise. We're probably saying the same thing and I have no idea if that holds any water or not.

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Re: Header primary pipe sequence into collector for 4/7 swap

Post by mk e » Wed Oct 04, 2017 2:01 pm

RevTheory wrote:
Wed Oct 04, 2017 12:21 pm
Whatever the sequence is, just hit the collector clockwise. We're probably saying the same thing and I have no idea if that holds any water or not.
I've never seen it specified on header designs....Just the lengths, dia of the tubes and colletors. Position in the collector is just based on routing the pipes to get the correct dimensions and avoid sharp bends whenever possible.....or so I've alway been told.
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Re: Header primary pipe sequence into collector for 4/7 swap

Post by grant6395 » Wed Oct 04, 2017 2:26 pm

When speeding to Calvin, he told me with a merge collector, on a high winding engine, counter, or clockwise isn't as important as having cyls firing next to each other, rather than across ..I did that when building mine and what a pain in the ass it was. Not sure if it made any difference, but I will never know.

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Re: Header primary pipe sequence into collector for 4/7 swap

Post by RevTheory » Wed Oct 04, 2017 2:47 pm

That whole clockwise deal never made any sense to me (although that doesn't mean anything)- I was just mentioning what I've read. In fact, I don't even remember where I read it.

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Re: Header primary pipe sequence into collector for 4/7 swap

Post by redliner » Wed Oct 04, 2017 4:00 pm

grant6395 wrote:
Wed Oct 04, 2017 2:26 pm
When speeding to Calvin, he told me with a merge collector, on a high winding engine, counter, or clockwise isn't as important as having cyls firing next to each other, rather than across ..I did that when building mine and what a pain in the ass it was. Not sure if it made any difference, but I will never know.
I thought perhaps a guy would want them to fire in a sequence which helps the closest one as it goes out... kinda... I dunno how to explain what I am thinking but it prolly doesnt make much of a difference .... I think perhaps at my level I will build them according to pipemax and route them with as sweeping and as few bends as possible and go from there....

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Re: Header primary pipe sequence into collector for 4/7 swap

Post by mk e » Wed Oct 04, 2017 5:24 pm

redliner wrote:
Wed Oct 04, 2017 4:00 pm
I think perhaps at my level I will build them according to pipemax and route them with as sweeping and as few bends as possible and go from there....
That sounds like a winning plan!

Programs like dynomation5 (just ordered my copy of dynomation6) or the designs I've seen from places like burns have having at all about order in the collector, but the flow bench and dyno sure say bends matter!
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Re: Header primary pipe sequence into collector for 4/7 swap

Post by redliner » Wed Oct 04, 2017 5:33 pm

mk e wrote:
Wed Oct 04, 2017 5:24 pm
redliner wrote:
Wed Oct 04, 2017 4:00 pm
I think perhaps at my level I will build them according to pipemax and route them with as sweeping and as few bends as possible and go from there....
That sounds like a winning plan!

Programs like dynomation5 (just ordered my copy of dynomation6) or the designs I've seen from places like burns have having at all about order in the collector, but the flow bench and dyno sure say bends matter!
What do they say about the order of the pipes in the collector for my 4/7 swap I'm wundrin...

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Re: Header primary pipe sequence into collector for 4/7 swap

Post by mk e » Wed Oct 04, 2017 5:38 pm

redliner wrote:
Wed Oct 04, 2017 5:33 pm
mk e wrote:
Wed Oct 04, 2017 5:24 pm

That sounds like a winning plan!

Programs like dynomation5 (just ordered my copy of dynomation6) or the designs I've seen from places like burns have having at all about order in the collector, but the flow bench and dyno sure say bends matter!
What do they say about the order of the pipes in the collector for my 4/7 swap I'm wundrin...
They don't care about the order of the pipes in ANY setup of any kind. Get the sizes right, use the biggest bends you can and you'll have a good header no matter what order they get plugged into the collect.
Mark
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