best header tube size??
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Melting Slicks
Joined: Aug 2004
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best header tube size??
Hi Guys
I know this has been kicked around here many times before, but I couldn't find it.
What is the best header tube size for on a 350 c.i. engine? Seems like there was something about if the tube size was too big ( 1 3/4" ?), you could lose power.
thanks in advance
I know this has been kicked around here many times before, but I couldn't find it.
What is the best header tube size for on a 350 c.i. engine? Seems like there was something about if the tube size was too big ( 1 3/4" ?), you could lose power.
thanks in advance
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
There is no simple answer to this question. Some people will tell you that 1 5/8" makes more low end power than 1 3/4" Personally I don't buy it. I've seen too many cars gain horsepower by going up in header size.
I've seen an LS1 gain torque all the way across the board by going from 1 3/4 to 1 7/8. If it did that then you know 1 5/8 would have cost it even more. Now a chassis dyno graph starts around 2000 RPM, so there may be some difference below that point, but believe me it's negligable.
Ultimately there is no blanket answer. If your engine only turns 5000 RPM's and you're running stock heads, yeah 1 5/8 headers might be OK. If you're turnning 6500 RPM's with a cam and good flowing heads then you'll probably really want the 1 3/4"s This is because what you gain on the top end may outweigh anything that you give up on the bottom end.
I hate to say it but go over to the f-body forums and take a look at the power that people are making on stock head cars with just cams and headers. They're all running 1 3/4. The 1 5/8 is better for low end torque thing seems to be common only to this forum. Every big HP car I've ever personally seen has 1 3/4 or larger.
I've seen an LS1 gain torque all the way across the board by going from 1 3/4 to 1 7/8. If it did that then you know 1 5/8 would have cost it even more. Now a chassis dyno graph starts around 2000 RPM, so there may be some difference below that point, but believe me it's negligable.
Ultimately there is no blanket answer. If your engine only turns 5000 RPM's and you're running stock heads, yeah 1 5/8 headers might be OK. If you're turnning 6500 RPM's with a cam and good flowing heads then you'll probably really want the 1 3/4"s This is because what you gain on the top end may outweigh anything that you give up on the bottom end.
I hate to say it but go over to the f-body forums and take a look at the power that people are making on stock head cars with just cams and headers. They're all running 1 3/4. The 1 5/8 is better for low end torque thing seems to be common only to this forum. Every big HP car I've ever personally seen has 1 3/4 or larger.
Drifting
Joined: Feb 2004
Posts: 1,485
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From: Champaign, IL
St. Jude Donor '05
Originally Posted by Nathan Plemons
The 1 5/8 is better for low end torque thing seems to be common only to this forum. Every big HP car I've ever personally seen has 1 3/4 or larger.
maybe people need the smaller diameter for backpressure if they're running open headers or straight pipes 
or maybe people spent $$ on smaller headers and don't want to admit they could be losing hp 
Team Owner
Joined: Sep 2002
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From: OBAMA IS HITLER
Originally Posted by Nathan Plemons
....The 1 5/8 is better for low end torque thing seems to be common only to this forum....
Also key is flow at the exhaust ports of your heads. Here's a formula for kicks, assuming you've got ported/good aftermarket heads:
Recommended primary diameter = The square root of: exhaust cfm at max valve lift X 1.27, then divided by a factor of 85.
Fun, eh? This is mathematical theory. Nathan tells it outright. But the whole gig is that if you've got extra ponies under the hood (heads, cam, exhaust.....and intake for the L98 guys), then for all intents & purposes get yourself a set of 1 3/4" headers........Sure 1 5/8" is great for an all stock C4 engine BUT if you have inkling that you'll be modifying it in the future, save yourself the agony of wasted $$ having to buy another set of headers (hey thats $600-$700 after full coating).....You'll definitely get SOTP bang now and it will increase even greater, later.
Ok my little sermon is over
P.S. I re-read the original post. You have an LT4, which is only inches away from the 1 5/8" vs. 1 3/4" line in full stock trim. If I were you, I wouldn't hesitate for a second in getting 1 3/4".
Now the sermon is really over
Last edited by Red Tornado; Feb 19, 2005 at 11:22 AM.
Team Owner
Joined: Oct 2004
Posts: 81,241
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From: altered state
St. Jude Donor '05
I've always stuck to 1 5/8 if its a sreet car for all-around torque; If it was a mostly strip/some track/track only, and had the cam, gears and heads to justify it, then 1 3/4 may be your answer. Depends on the car.
Which year motor/mods? Auto/Stick, gears? Maybe that would help
Edit:Seems you have the LT4-
Which year motor/mods? Auto/Stick, gears? Maybe that would help
Edit:Seems you have the LT4-
Last edited by cv67; Feb 19, 2005 at 11:28 AM.
Race Director
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From: The Top of Utah
Originally Posted by ToyC4
or maybe people spent $$ on smaller headers and don't want to admit they could be losing hp The smaller tubes will start to work at lower rpms. They will boost low speed power where the 1 3/4" won't. For any normally street driven 400 CID or smaller gen I or Gen II SBC, the 1 5/8ths" tubes will give up no power on the top end. I agree with the comment, above, concerning the header sizes on the LS engines. Those Gen III and Gen IV engines are a totally different animal than we C4 owners deal with. You will get a good gain with 1 3/4" headers. However, you will get a greater gain, over a wider rpm range, with 1 5/8ths" headers. If you aren't convinced by the rantings of a guy that doesn't even have headers, look up Jesse and Corkie, with their 10 second 434s and ask THEM what big headers did for them, and at what engine size. If you drive it at all, you want the smaller tubes. If you only race it, you want to look very closely at your set up, even so 1 5/8ths" will be the right choice for a 350.
RACE ON!!!
Large Impressive Member
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
I ain't got no dog in this fight, 
I've decided to be like Switzerland. 
Can't we all just get along? 
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Drifting
Joined: Jun 2002
Posts: 1,305
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From: Savannah Ga.
Originally Posted by CFI-EFI
I am one of the bigger advocates of the 1 5/8ths" headers. *I* don't even HAVE headers on my car, so that quote certainly doesn't apply to me. I think that is true of many of the guys with 1 3/4" headers. They've spent their money, received a gain, and they don't want to consider that they could have made a better decision.
The smaller tubes will start to work at lower rpms. They will boost low speed power where the 1 3/4" won't. For any normally street driven 400 CID or smaller gen I or Gen II SBC, the 1 5/8ths" tubes will give up no power on the top end. I agree with the comment, above, concerning the header sizes on the LS engines. Those Gen III and Gen IV engines are a totally different animal than we C4 owners deal with. You will get a good gain with 1 3/4" headers. However, you will get a greater gain, over a wider rpm range, with 1 5/8ths" headers. If you aren't convinced by the rantings of a guy that doesn't even have headers, look up Jesse and Corkie, with their 10 second 434s and ask THEM what big headers did for them, and at what engine size. If you drive it at all, you want the smaller tubes. If you only race it, you want to look very closely at your set up, even so 1 5/8ths" will be the right choice for a 350.
RACE ON!!!
The smaller tubes will start to work at lower rpms. They will boost low speed power where the 1 3/4" won't. For any normally street driven 400 CID or smaller gen I or Gen II SBC, the 1 5/8ths" tubes will give up no power on the top end. I agree with the comment, above, concerning the header sizes on the LS engines. Those Gen III and Gen IV engines are a totally different animal than we C4 owners deal with. You will get a good gain with 1 3/4" headers. However, you will get a greater gain, over a wider rpm range, with 1 5/8ths" headers. If you aren't convinced by the rantings of a guy that doesn't even have headers, look up Jesse and Corkie, with their 10 second 434s and ask THEM what big headers did for them, and at what engine size. If you drive it at all, you want the smaller tubes. If you only race it, you want to look very closely at your set up, even so 1 5/8ths" will be the right choice for a 350.
RACE ON!!!
MY MAN .....WHEN IT COMES TO HEADERS
OH SNAPS!!! NATHANS MY MAN WHHEN IT COMES TO LT1'S 
There is no simple answer to this question. Some people will tell you that 1 5/8" makes more low end power than 1 3/4" Personally I don't buy it. I've seen too many cars gain horsepower by going up in header size.
I've seen an LS1 gain torque all the way across the board by going from 1 3/4 to 1 7/8. If it did that then you know 1 5/8 would have cost it even more. Now a chassis dyno graph starts around 2000 RPM, so there may be some difference below that point, but believe me it's negligable.
Ultimately there is no blanket answer. If your engine only turns 5000 RPM's and you're running stock heads, yeah 1 5/8 headers might be OK. If you're turnning 6500 RPM's with a cam and good flowing heads then you'll probably really want the 1 3/4"s This is because what you gain on the top end may outweigh anything that you give up on the bottom end.
I hate to say it but go over to the f-body forums and take a look at the power that people are making on stock head cars with just cams and headers. They're all running 1 3/4. The 1 5/8 is better for low end torque thing seems to be common only to this forum. Every big HP car I've ever personally seen has 1 3/4 or larger.
Race Director
Joined: May 2001
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Originally Posted by CFI-EFI
look up Jesse and Corkie, with their 10 second 434s and ask THEM what big headers did for them,
The best answer to this question is simple. Buy whatever the hell damn header you want and then keep your opinion to yourself because lord help you if your opinion differs from somebody else.
Team Owner
Joined: Sep 2002
Posts: 22,209
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From: OBAMA IS HITLER
CFI-EFI, with all due respect to those who make a hobby out of it, I'm apt to subscribe to folks like David Vizard who's made it their 24-7 business to learn from a lifetime of research and engine development. And yeah, we're talking Gen I and II engines. When he says 375 gross hp with decent heads for 1.75" headers, then I'll take that to the bank.
See my post above.
See my post above.
Last edited by Red Tornado; Feb 19, 2005 at 03:16 PM.
Race Director
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From: Database Error Indiana
Originally Posted by Corvette Kid NC
I ain't got no dog in this fight, I've decided to be like Switzerland. Can't we all just get along?
Large Impressive Member
Joined: Jul 2003
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Originally Posted by Spankyellow
I laugh my butt off every time this debate comes up. Great entertainment on a cold winter day.
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by Nathan Plemons
And their cam choice and head numbers and desired RPM of operation all play major roles in that. They built their engines for torque, if they shift at 5000 RPM's every time out how would they know if they gained 50 horsepower at 6000 RPM's?
Originally Posted by Nathan Plemons
The best answer to this question is simple. Buy whatever the hell damn header you want and then keep your opinion to yourself because lord help you if your opinion differs from somebody else.
"...then keep your opinion to yourself because lord help you if your opinion differs from somebody else." I see you have failed to follow your own advice.
RACE ON!!!
Race Director
Joined: May 2001
Posts: 14,165
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Look, I gave my input, you gave yours. Now I advised the person to take his information and make his decision and then don't even bother letting anybody know what it is because SOMEBODY will tell him he made the wrong choice.
I'm not going to argue with you because it's not worth it. You're so convinced that you're right that you won't listen to any other points and likewise so am I. It's a waste of time to debate it any further.
Is that OK with you?
I'm not going to argue with you because it's not worth it. You're so convinced that you're right that you won't listen to any other points and likewise so am I. It's a waste of time to debate it any further.
Is that OK with you?
Large Impressive Member
Joined: Jul 2003
Posts: 65,811
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
To Nathan & CFI-EFI
It's common knowledge to anyone who's been on the forum for any time at all that this subject has been discussed ad nauseum. I'm not complaining because repetitive posts generally don't annoy me much. I just don't click on them. But I'll admit I always have to check this one out just because in all my years of messing with cars this has always been a topic of debate. And I'm never certainly too old to learn. That being said, I truly hope that you two will continue to respect each other and agree to disagree. You're both two of the people on this forum who's posts or threads I almost always check out, regardless of subject matter because I respect your thoughts and opinions that much. Although a lot of it has been in the parts for sale section, there's been a seemingly inordinate amount of bickering on the forum lately and I hope that two guys I've never met but consider friends won't hold a grudge over a disagreement on theory. This place is my internet family so this really matters to me.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Nathan Plemons
I'm not going to argue with you because it's not worth it. You're so convinced that you're right that you won't listen to any other points and likewise so am I. It's a waste of time to debate it any further.
Is that OK with you?
Is that OK with you?
Maybe I misinterpreted this paragraph as being directed at me:
Originally Posted by Nathan Plemons
The best answer to this question is simple. Buy whatever the hell damn header you want and then keep your opinion to yourself because lord help you if your opinion differs from somebody else.
RACE ON!!!