Header Primary Size Mathcing w/ Cam and Heads
Header Primary Size Mathcing w/ Cam and Heads I have always thought that with the more displacement you have, the larger headers you should get. For my 427, I was planning on getting 1-7/8" stepped to 2" with a 3.5" collector. However, there is a question of the exhaust velocity relative to the primary diameter. Obviously the larger diameter primary will have less exhuat velocity than a smaller header primary. My question is, how do you know when more velocity is better than more volume? I assume this may have something to do with the cam duration/lift/ramp rate as well as head exhaust port flow/velocity/volume. Thanks!
TECH Fanatic
Joined: Jun 2002
Posts: 1,979
Likes: 3
From: Upstate NY
Originally Posted by Ferocity02
I have always thought that with the more displacement you have, the larger headers you should get. For my 427, I was planning on getting 1-7/8" stepped to 2" with a 3.5" collector. However, there is a question of the exhaust velocity relative to the primary diameter. Obviously the larger diameter primary will have less exhuat velocity than a smaller header primary. My question is, how do you know when more velocity is better than more volume? I assume this may have something to do with the cam duration/lift/ramp rate as well as head exhaust port flow/velocity/volume. Thanks!
Another thing primary pipe diameter influences is torque peak rpm.
Have you heard of software called "PIPEMAX" ? It will help you a lot.
FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 6
From: Houston, Tx.
Originally Posted by Ferocity02
I have always thought that with the more displacement you have, the larger headers you should get. For my 427, I was planning on getting 1-7/8" stepped to 2" with a 3.5" collector. However, there is a question of the exhaust velocity relative to the primary diameter. Obviously the larger diameter primary will have less exhuat velocity than a smaller header primary. My question is, how do you know when more velocity is better than more volume? I assume this may have something to do with the cam duration/lift/ramp rate as well as head exhaust port flow/velocity/volume. Thanks!
FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 6
From: Houston, Tx.
Even the 1 7/8 Kooks seem to pick up on the 346 inchers whereas the small header cars always seem to be weaker and slower. Maybe the smaller headers are also not as nice in design and construction but invariably they seem to be weaker most of the time?
6600 rpm clutch dump of death Administrator
Joined: Dec 2001
Posts: 4,983
Likes: 13
From: Texas
Exhaust Valve Opens - EVO
Header pipe length (in inches) = ((850*(360-EVO))/RPM – 3
Header diameter (in inches) = ((cylinder. disp. * 16.38 / ((hdr len + 3) * 25))) * 2.1
These formulas are from A. Graham Bell’s Performance Tuning in Theory and Practice. For a street engine, the RPM used should be the peak torque RPM. For a race engine, the peak hp RPM should be used. For me, I've found that using the peak torque makes the headers way too long. So, I tend to stick with the peak HP number.
Header pipe length (in inches) = ((850*(360-EVO))/RPM – 3
Header diameter (in inches) = ((cylinder. disp. * 16.38 / ((hdr len + 3) * 25))) * 2.1
These formulas are from A. Graham Bell’s Performance Tuning in Theory and Practice. For a street engine, the RPM used should be the peak torque RPM. For a race engine, the peak hp RPM should be used. For me, I've found that using the peak torque makes the headers way too long. So, I tend to stick with the peak HP number.
Trending Topics
Originally Posted by 66deuce
does anyone make a 1-5/8" header for an LS1?considering the HP of a stock motor or even a mild H/C motor,it would seem that the 1-3/4" would be a little big.
I always asked the same thing. The one header I did try was headmens, its a 1 1/2 stepped to 1 5/8 header. Worked good.
Rick
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Originally Posted by Rick@Synergy
I always asked the same thing. The one header I did try was headmens, its a 1 1/2 stepped to 1 5/8 header. Worked good.
Rick
Rick
I would go with a set of LG 1 3/4 new f bod headers. They made 630 whp with their 1 3/4 header on an ls7 427. The torque curve was great and they stated that they would lose low end torque with a larger header and also only pick up maybe 5-10 whp.
Joined: May 2003
Posts: 377
Likes: 0
From: Fairfax County, VA (You know you're here when you see the bad roads)
LG makes a f-body header???? the only ones for f-body's I see on their website are hookers
Originally Posted by 52172
I would go with a set of LG 1 3/4 new f bod headers. They made 630 whp with their 1 3/4 header on an ls7 427. The torque curve was great and they stated that they would lose low end torque with a larger header and also only pick up maybe 5-10 whp.
