Header ?s
Thread Starter
Drifting
Joined: Nov 2001
Posts: 1,469
Likes: 6
From: 68 427 4.11s Roadster
Header ?s
Has anyone actually measured their primary lengths to see what they are and how closely matched they are?
What size engine or HP and what size primaries are you running?
Any reason why this size was chosen?
Collector diameter?
What size engine or HP and what size primaries are you running?
Any reason why this size was chosen?
Collector diameter?
Drifting
Joined: Oct 2003
Posts: 1,486
Likes: 10
From: Big Pine Key FL
Hooker header sidpipes and a 502 inch big block. The only thing that would sound better is a 600 inch BBC with a roots blower 
2.125 dia primaries 45" long 4" collector
I can waste a few HP, I drive torque! anyway I LOVE the sound, and I dont have to listen to the Fart Mufflers.
2.125 dia primaries 45" long 4" collector
I can waste a few HP, I drive torque! anyway I LOVE the sound, and I dont have to listen to the Fart Mufflers.
Drifting
Joined: Mar 2005
Posts: 1,806
Likes: 3
From: Burlington WI
Interesting article...
http://popularhotrodding.com/enginem...exh/index.html
Headers — Primary Pipe Lengths
Misconceptions concerning exhaust pipe lengths are widespread. Take for instance the much-overworked phrase “equal-length headers.” More than the odd engine builder/racer, or two, have made a big deal about headers with the primary pipes uniform within 0.5 inch. The first point this raises is whether or not what was needed was known within 0.5 inch! If not, the system could have all the pipes equally wrong within 0.5 inch! Trying to build a race header for a two-planed crank V-8 with lengths to such precision is close to a waste of valuable time. Under ideal conditions it is entirely practical for an exhaust system to scavenge at or near maximum intensity over a 4,000 rpm bandwidth. Most race engines use an rpm bandwidth of 3,000 or less rpm. If the primary pipe scavenging effect overlaps by 3,000 rpm then it matters little that one pipe tunes as much as 1,000 rpm different to another. Since this is the case, then all other things being equal, pipe lengths varying by as much as 9 inches have little effect
Headers — Primary Pipe Lengths
Misconceptions concerning exhaust pipe lengths are widespread. Take for instance the much-overworked phrase “equal-length headers.” More than the odd engine builder/racer, or two, have made a big deal about headers with the primary pipes uniform within 0.5 inch. The first point this raises is whether or not what was needed was known within 0.5 inch! If not, the system could have all the pipes equally wrong within 0.5 inch! Trying to build a race header for a two-planed crank V-8 with lengths to such precision is close to a waste of valuable time. Under ideal conditions it is entirely practical for an exhaust system to scavenge at or near maximum intensity over a 4,000 rpm bandwidth. Most race engines use an rpm bandwidth of 3,000 or less rpm. If the primary pipe scavenging effect overlaps by 3,000 rpm then it matters little that one pipe tunes as much as 1,000 rpm different to another. Since this is the case, then all other things being equal, pipe lengths varying by as much as 9 inches have little effect
Race Director
Joined: Nov 1999
Posts: 10,643
Likes: 8
From: Foxfield CO 1970 Convertible
From what I've read and seen (the PHR article was great), there are only general guidelines to follow when considering exhaust and headers. Exact measurements are not needed because the exhaust flow itself is not precise. It's also hard to measure exactly - for example: how do you measure the length of a header tube? on one side, on the other, or is the length an imaginary line through the center of the pipe? No one can measure a length exactly, so I think that within 1/2 in. is considered exact in the case of headers.
All exhausts are compromises based on requirements. In the case of my SB, I have the following exhaust system requirements:
- must have 1-3/4 in or greater tube size
- must have 3 in or greater exhuast pipe size
- must have fittings for O2 sensor
- must minimize restriction
- equal length header tubes would be nice
- must fit the physical requirements of a Vette
To meet most of my requirements, I had to drop the equal length criteria since it was of less importance than the others. I've purchased Sanderson 1-7/8 shorty headers, custom connection pipe with sensor bung to 4in side pipes.
All exhausts are compromises based on requirements. In the case of my SB, I have the following exhaust system requirements:
- must have 1-3/4 in or greater tube size
- must have 3 in or greater exhuast pipe size
- must have fittings for O2 sensor
- must minimize restriction
- equal length header tubes would be nice
- must fit the physical requirements of a Vette
To meet most of my requirements, I had to drop the equal length criteria since it was of less importance than the others. I've purchased Sanderson 1-7/8 shorty headers, custom connection pipe with sensor bung to 4in side pipes.
