Hi All,
running hilborn EFI 2 7/16 IR injection set-up on my 434 SBC in my canam replica. I have used the pipemax program ( PipeMax36xp2 ) in the construction of my headers and am now planning to use it to trim stack length so I tune to either the second or third harmonic. My engine is a low revver and was dyno'd at 595hp at 6300 and 565 ft/lbs at 4800 with a world products single plane intake and a 1050 dominator on it. I have the dyno data loaded into the software and am getting the following advice from the software (lengths are inches):
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- Induction System Tuned Lengths - ( Cylinder Head Port + Manifold Runner )
1st Harmonic= 35.097 (usually this Length is never used)
2nd Harmonic= 19.920 (some Sprint Engines and Factory OEM's w/Injectors)
3rd Harmonic= 13.907 (ProStock or Comp SheetMetal Intake)
4th Harmonic= 10.946 (Single-plane Intakes , less Torque)
Note> 2nd and 3rd Harmonics typically create the most Peak Torque
4th Harmonic is used to package Induction System underneath Hood
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I followed up with an email to Larry Meaux who advised that the third harmonic usually creates the most average torque across the range, and that the 2nd usually has the highest peak but is "peakier".
It is around 12 inches from the back of the intake valve to the top of the hilborn intake, meaning stack length will be 8 inches for second harmonic and only 2 inches for the supposedly broader curve delivered by 3rd harmonic tuning.
Clearly the original guys with the big stacks were tuning at or around the second harmonic ( http://rcd.typepad.com/rcd/2007_06_26_IMG_3412_20_28Small_29.jpg ), and did seem to have peakiness issues with the BBC until they went to staggered length to compensate for the BBCs two different intake port designs ( http://www.airportjournals.com/Photos/0609/X/0609022_7.jpg ).
My thinking is that an 8 inch stacks would look better and be more in keeping with cars of the day, but 2 inches might work better and would be easier to build a low profile plexi cold air box around.
Any experiences or thoughts?
Cheers, Andrew Robertson
running hilborn EFI 2 7/16 IR injection set-up on my 434 SBC in my canam replica. I have used the pipemax program ( PipeMax36xp2 ) in the construction of my headers and am now planning to use it to trim stack length so I tune to either the second or third harmonic. My engine is a low revver and was dyno'd at 595hp at 6300 and 565 ft/lbs at 4800 with a world products single plane intake and a 1050 dominator on it. I have the dyno data loaded into the software and am getting the following advice from the software (lengths are inches):
---------------------
- Induction System Tuned Lengths - ( Cylinder Head Port + Manifold Runner )
1st Harmonic= 35.097 (usually this Length is never used)
2nd Harmonic= 19.920 (some Sprint Engines and Factory OEM's w/Injectors)
3rd Harmonic= 13.907 (ProStock or Comp SheetMetal Intake)
4th Harmonic= 10.946 (Single-plane Intakes , less Torque)
Note> 2nd and 3rd Harmonics typically create the most Peak Torque
4th Harmonic is used to package Induction System underneath Hood
---------------------
I followed up with an email to Larry Meaux who advised that the third harmonic usually creates the most average torque across the range, and that the 2nd usually has the highest peak but is "peakier".
It is around 12 inches from the back of the intake valve to the top of the hilborn intake, meaning stack length will be 8 inches for second harmonic and only 2 inches for the supposedly broader curve delivered by 3rd harmonic tuning.
Clearly the original guys with the big stacks were tuning at or around the second harmonic ( http://rcd.typepad.com/rcd/2007_06_26_IMG_3412_20_28Small_29.jpg ), and did seem to have peakiness issues with the BBC until they went to staggered length to compensate for the BBCs two different intake port designs ( http://www.airportjournals.com/Photos/0609/X/0609022_7.jpg ).
My thinking is that an 8 inch stacks would look better and be more in keeping with cars of the day, but 2 inches might work better and would be easier to build a low profile plexi cold air box around.
Any experiences or thoughts?
Cheers, Andrew Robertson