Re: Header size?
[Re: gss]
#1689510
10/23/14 10:18 AM
10/23/14 10:18 AM
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Joined: Jan 2003
Posts: 13,362
Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,362
Marion, South Carolina [><]
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gss...I agree 100% w/ what was said already, a 1 3/4" or 1 7/8" header is what you need. Those 2 1/8" headers will kill the lowend on your motor. 
CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax
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Re: Header size?
[Re: an8sec70cuda]
#1689511
10/23/14 10:25 AM
10/23/14 10:25 AM
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Joined: May 2014
Posts: 503
Idaho
1320Dart
mopar
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mopar
Joined: May 2014
Posts: 503
Idaho
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How do you guys come up with header sizes? Is there a formula that you use?
Greg ----------------------------------------------------------------- Cost is irrelevant, making memories is far more valuable! 
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Re: Header size?
[Re: 1320Dart]
#1689512
10/23/14 10:47 AM
10/23/14 10:47 AM
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Joined: Nov 2009
Posts: 3,082
St. Paul , Mn.
tubtar
master
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master
Joined: Nov 2009
Posts: 3,082
St. Paul , Mn.
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Quote:
How do you guys come up with header sizes? Is there a formula that you use?
Yeah........it's called Mr. Peabody. 
He has a program ( pipemax ? )and was very generous in his assistance with mine and many others.
The Wallace calculator can give you a good baseline too.
http://www.wallaceracing.com/header_length.php
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Re: Header size?
[Re: gss]
#1689514
10/23/14 11:51 AM
10/23/14 11:51 AM
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Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
BradH
Taking time off to work on my car
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Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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Quote:
I understand all that. I just want to know the difference in horsepower and torque. There has to be countless dyno tests and dragstrip tests.
I'm sure there are some magazine tests done on header sizes that will give you a reasonable idea. Google can probably turn up a few.
Regardless, a header way too big for any given combination kills the torque curve... and the combination you described can't afford to give up torque with only 400 cubes.
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Re: Header size?
[Re: gss]
#1689516
11/03/14 04:32 PM
11/03/14 04:32 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
I have a mild 400, .528 solid cam, old DC Stage 4 heads. I can get a good deal on a set of headers with 2 1/8 primaries. What would I be giving up it terms of torque and horsepower using these headers vs a 1 3/4" primary? Full exhaust street car. Thank you
For your mild street car you would be giving up a lot
of torque with 2 1/8 pri. and mainly where you would
need it... 1 3/4 would work great for the street..
if you can.. set the collector length to about 18"
from the end of the primaries.. also measure the distance
to the front wall of the muffs... they should hopefully
be in multiples of that 18"(as in 18" 36" an so on)
for the best torque... in most cases(if not all) the
pri length is too long and the collector is to small
in dia and length).. if its 3" dia a 3.5" is normally
better but being a street car I wouldnt worry about it
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Re: Header size?
[Re: gss]
#1689518
11/04/14 12:51 AM
11/04/14 12:51 AM
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Joined: Jan 2003
Posts: 16,925
NC
440Jim
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,925
NC
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Quote:
I have a mild 400, .528 solid cam, old DC Stage 4 heads. I can get a good deal on a set of headers with 2 1/8 primaries. What would I be giving up it terms of torque and horsepower using these headers vs a 1 3/4" primary? Full exhaust street car. Thank you
As others have said, you would get killed in torque below 5500 rpm. And below 4000 rpm would be really bad. There is no way I would run a header that big in dia in your combo.
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