Scavenging vs non scavenging

[TexasT]

"Back in the day" design....

MICKEY THOMPSON SUPER SCAVENGER HEADERS

www.chevelles.com

But they have a very distinct sound and I'd run a set if I had em.

 

[xlr8ngn]

What a rabbit hole. I've been reading about multiple stepped turbo headers with negative pulse tuning at both peak HP and peak torque. Good stuff to know that I will probably never incorporate myself, but helps when understanding and selecting between manufacturers of our products.

 

[Chuck Leeper]

What a rabbit hole. I've been reading about multiple stepped turbo headers with negative pulse tuning at both peak HP and peak torque. Good stuff to know that I will probably never incorporate myself, but helps when understanding and selecting between manufacturers of our products.

A good engine dyno, LOTS of tubing, CNC bender, tig, flow bench, all required for the testing.
You know, something like free reign in a NASCAR development facility!
Would be nice to have access to all that "stuff".
In a more "simplistic realm", the GM cast steel exh manifolds make an easy 1000Hp on a J/Y LS/Vortec engine.
Like the set I fabbed here at home shop....

 

[TIMINATOR]

The Super Scavengers worked because they were equal length and had long primary tubes. What they didn't have was much scavenging, because the tube ends were all different lengths and the box collector was of a larger area than a normal collector, decreasing the vacuum on the other longer and shorter pipes. The long primary tubes were designed to peak in the midrange for 2 reasons. The lousy tires didn't have much traction, so the power came on once the tires hooked up, so they felt powerful, and mid range is where most of your driving is done, so they felt powerful on the street.
Most modern Street headers have primary lengths that are about 10 to 14 inches different lengths, reducing the "peak effect." But they do scavenge better and exhibit a wider, but lower peak power.
Race headers are usually within 4 to 7 inches, with the best ones within a few inches in primary difference.
Typically headers within an inch or two on the primaries, run over $1000, but they are available. The set for my street/strip Challenger cost $1400 with shipping, but it should run high 8s with power steering, brakes, windows, and A/C, drive it to the track.
When I build headers for a 4 speed car, I set the tube length for the launch RPM, and the diameter and collector length for the upper end. On my Pinto 2.3 motor, that worked perfectly with the intake tuned length (Weber carbs with stacks) set for the last 700 RPM before the shift point.
Back to turbo stuff, the freer flowing headers and crossover tube (don't go too big on the x over, as it drops the exhaust gas speed and temperature, wasting energy) with everything else equal will make the most power. A larger diameter x over favors upper end HP, while a smaller diameter favors response and spool time.
Coated headers and crossover make more power and better transient response, and on a turbo car, it's worth it!
TIMINATOR
P.S. those cast manifolds look like they were designed for turbo use!