Long tube headers use sonic pulses to tune the exhaust to scavenge cylinder to make power.
This has NO direct connection with backpressure, that's **Totally** different.
Short tubes are not headers. They are tube replacements for stock manifolds.
You can search for this, gets asked all the time.
: 1 1/2” OR 1 5/8” x Modern Performance
don’t know: “This is determined at the factory.”
: OLD: 1 3/4” x 27” 3" collector
Has .1" thick pipe walls ... < than a conventional 1 5/8" Inside diameter.
NEW AF/x: Same dimensions, thin wall tubes.
: 1 5/8 x 25” 2.5” collector $174-309Write up on b .org
*MPP: Stainless medium length
*Fast Fabs/MadDog: Some 1 7/8” These’re best because they’re not available.
* Self Fabs, ie, Burns Stainless
Most headers come w/ a 'Dump' collector.
Merge collectors force each pulse to follow the other as the design forces the tubes to exit thru a common pipe, instead of one large chamber.
The new collector is the 'merge' collector. It adds a couple percent hp;
Note the v-band clamp; doesn't add any power, but seals better and has more clearance!
You will need a solid booger bobble to keep the collector from breaking. We sell fancy ones, Vitor sells some also.
They also act as a roll-jack to increase collector to ground clearance.
Some have tapped the original damper and filled it w/ grease.