Equal length vs Non equal length headers?
Thread Starter
Race Director
Joined: Nov 2000
Posts: 16,416
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From: NC,USA
Equal length vs Non equal length headers?
Hey guys...
I'm thinking about installing some hooker side pipes on the 75... but the question that has come to mind is wheither or not they are equal length pipes! If they arent then ya dont get the same environment in each cylinder... but if ya have em the same length ya can tune the motor to a higher degree.
On the other hand... If they are not equal length then I'm probably not losing much power on a 350 small block setup for semi-mild street use, but I'd like to upgrade in the future! Stahl headers/sidepipes sure do look nice, but the wallet says no to that at the moment....
So, Is the jury out on the length of the hookers? Or are they all show and less go then whats possible with under car setups? Without a crossover pipe ya lose a little power... but you might gain some from just having less pipe overall :confused:
I'm thinking about installing some hooker side pipes on the 75... but the question that has come to mind is wheither or not they are equal length pipes! If they arent then ya dont get the same environment in each cylinder... but if ya have em the same length ya can tune the motor to a higher degree.
On the other hand... If they are not equal length then I'm probably not losing much power on a 350 small block setup for semi-mild street use, but I'd like to upgrade in the future! Stahl headers/sidepipes sure do look nice, but the wallet says no to that at the moment....
So, Is the jury out on the length of the hookers? Or are they all show and less go then whats possible with under car setups? Without a crossover pipe ya lose a little power... but you might gain some from just having less pipe overall :confused:
Team Owner
Joined: Jul 1999
Posts: 65,492
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From: Orange Park Florida
Re: Equal length vs Non equal length headers? (ZD75blue)
I talked with one of the smart guys at Schoenfled headers.com one time, and specifically asked about equal vs unequal length headers....he said the dyno guys LOVE equal length headers.....
BUT for some reason CARS love unequal length, meaning they win more....
go figger....
I asked which was better with a stock just muffler, no cat, '72 exhaust system...he laughted and said NO differance, we swore....NO differances....
he said any exhaust system after the header negated so much of any gains from headers, that he thought they were about useless.....this from a smart guy at a header manufacturer....
but then again, Schoenfeld is into racing class cars at tracks, not street machines...but I think he is right.....
GENE
BUT for some reason CARS love unequal length, meaning they win more....
go figger....
I asked which was better with a stock just muffler, no cat, '72 exhaust system...he laughted and said NO differance, we swore....NO differances....
he said any exhaust system after the header negated so much of any gains from headers, that he thought they were about useless.....this from a smart guy at a header manufacturer....
but then again, Schoenfeld is into racing class cars at tracks, not street machines...but I think he is right.....
GENE
Le Mans Master
Joined: Jun 2002
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From: I can walk to MA
Re: Equal length vs Non equal length headers? (ZD75blue)
I'm no exhaust expert, but I believe the equal length primary pipes help
exhaust flow. This is because each cylinder puts out a burst of exhaust
pressure. If equal length, then the burst come in order. If unequal, then they
can arrive at the collector at the same time and basically push each other back.
There may be more to it, but that's what I understand.
:seeya
[Modified by NHvette, 11:28 PM 2/14/2004]
exhaust flow. This is because each cylinder puts out a burst of exhaust
pressure. If equal length, then the burst come in order. If unequal, then they
can arrive at the collector at the same time and basically push each other back.
There may be more to it, but that's what I understand.
:seeya
[Modified by NHvette, 11:28 PM 2/14/2004]
Melting Slicks
Joined: Jul 2002
Posts: 3,000
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From: Boulder Creek California
Re: Equal length vs Non equal length headers? (NHvette)
My Hooker Comp headers are waiting for me in NC, anybody know if they're equal or not?? I don't remember from looking at them.
I run a pretty open exhaust, although I do still have tubes behind the headers, and insignificant mufflers. I would think there'd be a bit of a gain there. But I wouldn't consider buying equal length headers to replace unequals, as that money would have a far far greater effect just about anywhere else!
-Chris
I run a pretty open exhaust, although I do still have tubes behind the headers, and insignificant mufflers. I would think there'd be a bit of a gain there. But I wouldn't consider buying equal length headers to replace unequals, as that money would have a far far greater effect just about anywhere else!
-Chris
Instructor
Joined: Mar 2003
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From: Lawrenceville GA
Re: Equal length vs Non equal length headers? (RUXperienced)
The way is has been explained to me is that the difference between the two were so small on a street car that the extra money spent on equal lengths would be a waste
Drifting
Joined: Oct 2000
Posts: 1,825
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From: Shawano WI
Re: Equal length vs Non equal length headers? (mrvette)
Gene: Your right, Don Schoenfeld is a great guy to talk to about headers. And anything he says you can take for gospel because he will have hard data to back it up. (unless he says "lets just stop for one or two drinks" after a Razorback game, then you know you are going to wake up with a BIG headache the next morning :yesnod: ) and he makes a darn good header also.
There are no equal lenght headers on street cars. There may be "close to equal lenght" but no true equal lenght headers. There just is not enough room to do it. You can take a tape measure and measure the primary tube and you will find that they will be lucky for the tubes to be within 2" of each other in lenght. There are very few race car headers that are true equal lenght. you have to get into the 3K to 5K price range to get a true equal lenght primary tube.
And Schoeneld is correct in that the minute you put any muffler on an exhaust system you loose the benifit you gain from a equal lenght or close to equal lenght header.
It is far more important to get the average primary lenght/collector lenght matched to the heads/cam/intake/RPM/compression combination that you are runnng, than it is to worry about equal lenght primaries.
There are no equal lenght headers on street cars. There may be "close to equal lenght" but no true equal lenght headers. There just is not enough room to do it. You can take a tape measure and measure the primary tube and you will find that they will be lucky for the tubes to be within 2" of each other in lenght. There are very few race car headers that are true equal lenght. you have to get into the 3K to 5K price range to get a true equal lenght primary tube.
And Schoeneld is correct in that the minute you put any muffler on an exhaust system you loose the benifit you gain from a equal lenght or close to equal lenght header.
It is far more important to get the average primary lenght/collector lenght matched to the heads/cam/intake/RPM/compression combination that you are runnng, than it is to worry about equal lenght primaries.
Drifting
Joined: May 2003
Posts: 1,634
Likes: 2
From: Melbourne, Victoria, Australia, the World
Re: Equal length vs Non equal length headers? (Pete79L82)
there is one guy in our club who is running equal length headers. His are Nascar style in that there are two tubes crossing over to the other side to join the other collector. The exhaust note is entirely different in that it sounds like a rotary or similar. he gets another 500 rpm out of the motor this way.
The run of the mill Headers which have the 4 pots on each side are not phased correctly and it does not matter if they are matched or correct length because the pulses from the cylinders will not be in phase. 18436572 firing order is not perfect. The odds and evens are not evenly spaced.
:cheers:
The run of the mill Headers which have the 4 pots on each side are not phased correctly and it does not matter if they are matched or correct length because the pulses from the cylinders will not be in phase. 18436572 firing order is not perfect. The odds and evens are not evenly spaced.
:cheers:
C6 the C5 of tomorrow
Joined: Nov 2000
Posts: 6,665
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From: Twin Cities Minnesota
Re: Equal length vs Non equal length headers? (Pete79L82)
Mine are as equal length, as close as I can measure with a tape measure!
They are side exhaust 1 3/4" x 36" long with a 3" merge collector.
Of course I built them myself spending way too much time :rolleyes:
I went from Headdman side exhaust headers with about 18" difference from longest to shortest. The car was darn near untuneable. You change the idle mixture screws and no diff on the vacuum gauge :mad
With the new equal length headers a 1/4 turn on any mixture screw makes a noticeable difference :cool:
That said I guess I must agree that as long as the headers are close to equal length (+- 1") you probably won't notice any difference in tuneability or power.
Also remember that that power is only going to be noticeable at WOT, cruzing around town, it don't matter.
They are side exhaust 1 3/4" x 36" long with a 3" merge collector.
Of course I built them myself spending way too much time :rolleyes:
I went from Headdman side exhaust headers with about 18" difference from longest to shortest. The car was darn near untuneable. You change the idle mixture screws and no diff on the vacuum gauge :mad
With the new equal length headers a 1/4 turn on any mixture screw makes a noticeable difference :cool:
That said I guess I must agree that as long as the headers are close to equal length (+- 1") you probably won't notice any difference in tuneability or power.
Also remember that that power is only going to be noticeable at WOT, cruzing around town, it don't matter.
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Melting Slicks
Joined: Jul 2002
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From: Boulder Creek California
Re: Equal length vs Non equal length headers? (78 Vette)
I would be more concerned about the 1 7/8 primaries on the Hookers killing your low end power on a mild motor.
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Re: Equal length vs Non equal length headers? (RUXperienced)
I doubt it's worth getting excited about for 95% of our stuff that's out here.
There are even interesting trends in short track roundy pounder racing (can you say mid range tq) that has purposely designed unequal length headers, different cam lobes and timing for different cylinders and different intake tracks all designed to spread out the powerband and broaden it. Might not make the most peak HP....but average will greatly improve. As he said...."cars like em".
There were even old tunnel rams for big blocks that had drastically different sized intake runners to compensate for the "good/bad" ports that all big blocks have. Makes sense that the exhaust requirements would likely be different too.
Once you really get into working out a new combo, this stuff can all be manipulated.
JIM
[Modified by 427Hotrod, 3:58 PM 2/15/2004]
There are even interesting trends in short track roundy pounder racing (can you say mid range tq) that has purposely designed unequal length headers, different cam lobes and timing for different cylinders and different intake tracks all designed to spread out the powerband and broaden it. Might not make the most peak HP....but average will greatly improve. As he said...."cars like em".
There were even old tunnel rams for big blocks that had drastically different sized intake runners to compensate for the "good/bad" ports that all big blocks have. Makes sense that the exhaust requirements would likely be different too.
Once you really get into working out a new combo, this stuff can all be manipulated.
JIM
[Modified by 427Hotrod, 3:58 PM 2/15/2004]
Thread Starter
Race Director
Joined: Nov 2000
Posts: 16,416
Likes: 1
From: NC,USA
Re: Equal length vs Non equal length headers? (427Hotrod)
I doubt it's worth getting excited about for 95% of our stuff that's out here.
There are even interesting trends in short track roundy pounder racing (can you say mid range tq) that has purposely designed unequal length headers, different cam lobes and timing for different cylinders and different intake tracks all designed to spread out the powerband and broaden it. Might not make the most peak HP....but average will greatly improve. As he said...."cars like em".
There were even old tunnel rams for big blocks that had drastically different sized intake runners to compensate for the "good/bad" ports that all big blocks have. Makes sense that the exhaust requirements would likely be different too.
Once you really get into working out a new combo, this stuff can all be manipulated.
JIM
[Modified by 427Hotrod, 3:58 PM 2/15/2004]
There are even interesting trends in short track roundy pounder racing (can you say mid range tq) that has purposely designed unequal length headers, different cam lobes and timing for different cylinders and different intake tracks all designed to spread out the powerband and broaden it. Might not make the most peak HP....but average will greatly improve. As he said...."cars like em".
There were even old tunnel rams for big blocks that had drastically different sized intake runners to compensate for the "good/bad" ports that all big blocks have. Makes sense that the exhaust requirements would likely be different too.
Once you really get into working out a new combo, this stuff can all be manipulated.
JIM
[Modified by 427Hotrod, 3:58 PM 2/15/2004]
What I've been thinking is that I want to setup the car to the best of my ability for now and the future... Currently its not in the budget to build a full race motor, but in the future it might be! So when the cost is less then half more to get a high end product, I'm jumping for the high end one.
That being said, I do like the look of side pipes, but tend to take ride and performance before looks :yesnod:
I guess I will have to make some calls to find out if the hookers are equal length, because if they arent even close then I'd rather find that out now then later!
:cheers:
How many hours did it take total to weld em up 427 V8?
:cool:
C6 the C5 of tomorrow
Joined: Nov 2000
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From: Twin Cities Minnesota
Re: Equal length vs Non equal length headers? (ZD75blue)
snip---
:cheers:
How many hours did it take total to weld em up 427 V8?
:cool:
Believe me, the Stahl's are cheap! LOL
And really if you're not a nut like me, or looking for every last HP stock exhaust is just fine.
Team Owner
Joined: Sep 2003
Posts: 88,393
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From: eville in
Re: Equal length vs Non equal length headers? (ZD75blue)
IMO to be EQUAL all tube's need to be same length AND SAME BENDS so
all need to flow the same CFM so test each tube after necessary bends and
modify to get into a collector, so for a street car using a wide RPM range
tube's that are close in length don't bother men
all need to flow the same CFM so test each tube after necessary bends and
modify to get into a collector, so for a street car using a wide RPM range
tube's that are close in length don't bother men
Drifting
Joined: Jan 2002
Posts: 1,500
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From: N.Y
Re: Equal length vs Non equal length headers? (RUXperienced)
I would be more concerned about the 1 7/8 primaries on the Hookers killing your low end power on a mild motor.
Are you referring to me? I should've been clearer, I didn't get super-comp headers, just the smaller Competition ones. I think they are 1-5/8" diameter?
Are you referring to me? I should've been clearer, I didn't get super-comp headers, just the smaller Competition ones. I think they are 1-5/8" diameter?
