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Best primary length for 6500 rpms?

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Old 07-06-2012, 05:51 AM
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Default Best primary length for 6500 rpms?

I am looking at building a set of headers for my project. What would be considered a good primary length to make good power around 6500 rpm? This would be for an L92 headed 6.0L with a street cam (224/228 possibly larger in the future). I am thinking of going with 1.75" diameter tubing. I will probably be walking that line between whether 1 5/8 would be better than 1 3/4 but I dont want to build more than one set of headers. Infact the whole concept of me building my own headers is a bit intimidating to me. But if thats a hoop I have to jump through then I guess Ill have to do it.

TIA: jay
Old 07-06-2012, 07:08 AM
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Good question! Hopefully someone has some input on this lol.
Old 07-09-2012, 07:49 AM
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I was hoping someone might have a computer HP estimate program that might allow you to tweak some header numbers.
Old 07-09-2012, 12:05 PM
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Seems like you really should just go with a common primary length. The torque/HP tradeoff usually comes with collector length. If you will be running an exhaust system, I'd be more concerned with where to put the X/H pipe.
Old 07-09-2012, 06:55 PM
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I used my Pipemax Software and with the little info you provided, these are the Dims I got,

16 guage tubing
-- 1.75in dia tubing
-- 28in - 31in primary length
-- 3in dia collector, 17in - 18in length

Hope this helps
Old 07-09-2012, 10:12 PM
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Ty 3rdgen. To be honest I have never used one of those programs and had no clue what info would be needed. I am kind of surprised that it calls for such a long collector tho.

TY for the input
Old 07-15-2012, 07:55 AM
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Not expensive...........

http://maxracesoftware.com/pipemax36xp2.htm
Old 08-25-2012, 10:39 PM
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[QUOTE=3rdGenLS;16500883]I used my Pipemax Software and with the little info you provided, these are the Dims I got,

16 guage tubing
-- 1.75in dia tubing
-- 28in - 31in primary length
-- 3in dia collector, 17in - 18in length


I'm trying to see how that relates to the displacement of the engine. So, I'll just show you my thought process here.

6.0 liters>366 cubic inches

366/8 = 45.75 cu-in per cylinder.

"What cylindrical length will give me 45.75 cubic inches with 1.75" I.D. tubing"

45.75/((1.75^2)*.25*pi) = 19"

Pipemax said 28-31". The 19" is a column equal to one cylinder volume at room temperature, and that makes it a harmonic length before the collector.

I remember engineering said "avoid harmonics", so I multiplied 19" by 1.5 to get 28."

Will the program re-translate that into 1 5/8" tubing, or does it demand 1.75" tube?



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