Quote:
Originally Posted by blueovalz
Thanks for sharing that with us Andrew. Have you already posted the results of your program on header tube length. If not, I'm sure they would also be of interest.
Terry

Hi Terry,
here is the header recommendation for engine from the Pipemax program:

 Single Primary Pipe Specs  for 433.893 CID from 4300 to 6800 RPM
Diameter= 1.807 to 1.932 Length= 31.8 to 34.6 inches long
 2Step Primary Pipe Specs 
1st Dia. inches= 1.807 Length= 15.9 to 17.3
2nd Dia. inches= 1.932 Length= 15.9 to 17.3
 3Step Primary Pipe Specs 
1st Dia. inches= 1.807 Length= 15.9 to 17.3
2nd Dia. inches= 1.932 Length= 7.9 to 8.6
3rd Dia. inches= 2.057 Length= 7.9 to 8.6
 Header Collector Specs (Conventional Straight Tube) 
Diameter= 3.309 to 3.559 Tuned Lengths= 17.9 best and also 9.0 or 35.8
 Header Collector Specs (Megaphone or Diffuser Cone Shape) 
Diameter= 2.809 taper to 3.809 Megaphone/Diffuser Length= 17.9 inches
Best HP/TQ Tuned Collector Lengths= 17.9 , 35.8 , 71.6 , 143.3 inches long
Worst HP/TQ Loss Collector Lengths= 26.9 , 53.7 , 107.5 , 214.9 inches long
Note> all Pipe Diameters are OD and basedoff .0625 inch Pipe thickness
 Primary Pipe's Harmonics 
1st Harmonic = 138.8 inches long ... typically never used
2nd Harmonic = 52.9 inches long ... longest recommended
3rd Harmonic = 31.8 inches long ... highly recommended , best Torque Curve
4th Harmonic = 22.2 inches long ... shortest recommended
5th Harmonic = 16.8 inches long ... typically never used
6th Harmonic = 13.3 inches long ... typically never used
7th Harmonic = 10.9 inches long ... typically never used
8th Harmonic = 9.0 inches long ... typically never used
 Collector's Harmonics (includes Intermediate, Muffler , TailPipe) 
1st Harmonic = 143.3 inches long ... longest with Mufflers and TailPipes
2nd Harmonic = 71.6 inches long ... longest recommended with Mufflers
3rd Harmonic = 35.8 inches long ... more bottomend Torque
4th Harmonic = 17.9 inches long ... highly recommended , best Torque Curve
5th Harmonic = 9.0 inches long ... reduced Torque , more topend HP sometimes
6th Harmonic = 4.5 inches long ... reduced Torque , not recommended

based on this I built a nonstepped design with 32 inch primaries in 1 7/8 inch, and an 18 inch collector into a chambered muffler which I treated as the end point in the system because of it's volume.
Cheers, Andrew