8-4-1 Headers (Video)

[TreeFiddyAre]

I have to say I'm a bit baffled by the idea of putting this 8-4-1 exhaust on a GT350 with a Voodoo FPC engine. The whole point of 8-4-1 is to create an FPC sound with a CPC engine. An FPC engine doesn't need that arrangement to sound like an FPC engine - it is one!

If you find some Youtube videos of the 1967 GT40's, they had 7 liter CPC engines but they sound very FPC, and that's because the cylinder heads had were reversed with the exhaust ports in the valley. That allowed the headers to reside in the valley above the block with the runners arranged so each header had balanced exhaust pulses, just like an FPC has.

So putting an 8-4-1 on a Voodoo won't make it sound more like an FPC engine because it already is one. All it can really do is change the "tone" of the exhaust - higher pitch or something, just like any other aftermarket Voodoo exhaust.

If that's wrong, what am I missing? Is this really about people with Coyote swaps fixing the sound?

Fair question—and you’re not wrong on the fundamentals.

I’m not chasing “make an FPC sound like an FPC.” The Voodoo already does that naturally, chaos and all. What I am after is manipulating pulse interaction, scavenging characteristics, and harmonic content to bias the exhaust toward a cleaner, higher-frequency pitch rather than just “louder Voodoo with more crackle.”

An 8-4-1 on an FPC isn’t about fixing firing order acoustics—it’s about how pulses pair, merge, and decay downstream. By controlling collector timing and reducing destructive interference between banks, you can shift the dominant harmonics upward. Think less thunderous baritone, more mechanical shriek at high RPM. Same song, different EQ.

As for power—any gain is gravy. If it picks up a few ponies from improved scavenging at elevated engine speeds, great. If not, I’ll survive. This isn’t a dyno-queen optimization exercise; it’s an acoustic engineering experiment with a side of “because racecar. ”But I have a feeling this system will produce great numbers down the road.

And yes… once it’s force-fed, the rate of RPM climb becomes the real party trick. If the exhaust can keep up with that kind of acceleration without turning into a metallic blender full of bolts, I’ll consider it a win. If not, well—the forum will get its 10-page thread anyway

So no, not about Coyotes trying to fake a flat-plane. It’s about seeing just how high-strung and unhinged a GT350 can sound before physics files a noise complaint.

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[Bulldogs22]

Curious how the design in managing the NVH from the Voodoo. OEM dampers are incorporated into the cat pipes and this design doesn’t have cats to begin with. Real test will be people who track multiple sessions back to back

 

[TreeFiddyAre]

Curious how the design in managing the NVH from the Voodoo. OEM dampers are incorporated into the cat pipes and this design doesn’t have cats to begin with. Real test will be people who track multiple sessions back-to-back

Another valid concern, and honestly one of the things I’m most curious about as well.


I’ll definitely report back once the system is installed and gets some real seat time—especially how the NVH translates through the chassis and into the cabin under sustained load. Short pulls are one thing; back-to-back sessions are where harmonics either behave… or start sending invoices. I won’t be tracking the car for now, but if the opportunity comes up, I’ll absolutely report any findings (or lack thereof).

That said, it’s worth noting we now have a large number of data points from traditional long-tube setups running without OEM dampers, and so far I personally haven’t seen widespread reports of adverse effects. Cracked welds and major issues seem to be the exception, not the rule.

As a contingency, I’ve already thought this through: if the harmonic content turns out to be a little too enthusiastic, the plan would be to section in the OEM dampers as close to their factory locations as possible. Basically a “have fire extinguisher, will weld” strategy. Best case, they stay on the shelf forever as expensive paperweights. Whether integrating them exactly where OEM placed them would even be the right move? No idea—but I’m hoping I won’t need to find out.

Performance-wise, I firmly believe there may be some surprising metrics from this system as a whole. Yes, the primaries aren’t traditional long-tube length—but that doesn’t automatically mean “no gains,” especially when you factor in collector design, secondary length, pulse pairing, and overall system flow. This is pure speculation on my part, but my gut says this setup could really be the jam for the Voodoo.

Also worth mentioning: it’s a true 3” system after the secondaries—mufflers included. There’s power to be found there alone, especially once boost enters the chat. From what I’ve seen, the OEM mufflers neck down internally to roughly 2.25” and include some fairly sharp turns before the exhaust gases are politely asked to leave the building. That’s not ideal when the engine is force-fed and trying to exhale at an alarming rate.

So worst case? We learn something new about pulse behavior, harmonics, and NVH. Best case? Cleaner scavenging, higher pitch, faster revs, and a Voodoo that sounds louder and more refined than it left the assembly line.

Either way, I’m really, reallyyyy salivating to get my mitts on this system—for science, of course
And I’m genuinely curious how the altered pulse pairing and collector geometry interact with the Voodoo’s inherent vibration profile.

Worst case scenario? Data.
Best case? Glorious mechanical controlled explosions with acceptable NVH.

 

[galaxy]

…aaannddddd it looks spectacular. There, I’ll say it.

 

[TreeFiddyAre]

…aaannddddd it looks spectacular. There, I’ll say it.

Oh yeah I forgot that part

 

[TreeFiddyAre]

Hi Gt350(R) posse!

I just got the following in from Concept 8-4-1 :


1) The flat 4-1 collector, while cool and different it is not optimal for sound. The quick split into two separate pipes doesn't allow a thorough mixing of both banks.

2) The extra long midpipe had too much volume which resulted in low exhaust velocity and dulled some of the sound. We tested it with a single larger diameter pipe and there was a noticeable improvement.

3) The O2 sensors were previously only taking readings from one secondary (two banks). The updated design gets O2 readings from all 4 cylinders per bank now.

4) A catted version will now be available using four cats.

5) We made the headers modular. The headers can be converted to equal length tri-ys for a different sound ( this will be later in the year )

6) GT500 kit will be plug and play. No more oil pan trimming

Looks like we’re trending for April. If you’ve preordered your system and want to see what the new setup looks like, hit him up—he’ll send over the CAD drawings. Much cleaner and more purposeful than the former design.

The engineering here screams pulse harmonics, scavenging efficiency, and “my car now sounds like an angry war god.” Totally worth the wait. This isn’t just louder, it’s engineered chaos—pulse harmonics tuned to evolve from angry war god to screaming banshee at redline. Basically a flat-plane violin being possessed.

Achilles warned us: “That’s why nobody will remember your name.”
Concept 8-4-1 clearly took that personally----This exhaust politely disagrees at 120 dB lol


Yeahhh I'm excited!! Happy Sunday everyone. The TreeFiddyAre gets an oil change in a couple of hours

 

[Bulldogs22]

Hi Gt350(R) posse!

I just got the following in from Concept 8-4-1 :


1) The flat 4-1 collector, while cool and different it is not optimal for sound. The quick split into two separate pipes doesn't allow a thorough mixing of both banks.

2) The extra long midpipe had too much volume which resulted in low exhaust velocity and dulled some of the sound. We tested it with a single larger diameter pipe and there was a noticeable improvement.

3) The O2 sensors were previously only taking readings from one secondary (two banks). The updated design gets O2 readings from all 4 cylinders per bank now.

4) A catted version will now be available using four cats.

5) We made the headers modular. The headers can be converted to equal length tri-ys for a different sound ( this will be later in the year )

6) GT500 kit will be plug and play. No more oil pan trimming

Looks like we’re trending for April. If you’ve preordered your system and want to see what the new setup looks like, hit him up—he’ll send over the CAD drawings. Much cleaner and more purposeful than the former design.

The engineering here screams pulse harmonics, scavenging efficiency, and “my car now sounds like an angry war god.” Totally worth the wait. This isn’t just louder, it’s engineered chaos—pulse harmonics tuned to evolve from angry war god to screaming banshee at redline. Basically a flat-plane violin being possessed.

Achilles warned us: “That’s why nobody will remember your name.”
Concept 8-4-1 clearly took that personally----This exhaust politely disagrees at 120 dB lol


Yeahhh I'm excited!! Happy Sunday everyone. The TreeFiddyAre gets an oil change in a couple of hours

Now this is an update we all can appreciate!

 

[TreeFiddyAre]

Here are the CAD of the new system :

 

[honeybadger]

Here are the CAD of the new system :

Any idea if those are for the GT350-specific system? Try to decode the cylinder pairings and looks like they're using a couple different.

The first/second pic has cylinders 1 +3 paired, and 2 + 4 paired on the passenger side. But then it looks like its pairing 5/6 and 7/8 on the driver side. But then the third picture pairs 5/7 and 6/8.

Curious to see what the final pairing. Hopefully its (1+3, 2+4, 5+7, and 6+8) for the Voodoo kit

 

[TreeFiddyAre]

Any idea if those are for the GT350-specific system? Try to decode the cylinder pairings and looks like they're using a couple different.

The first/second pic has cylinders 1 +3 paired, and 2 + 4 paired on the passenger side. But then it looks like its pairing 5/6 and 7/8 on the driver side. But then the third picture pairs 5/7 and 6/8.

Curious to see what the final pairing. Hopefully its (1+3, 2+4, 5+7, and 6+8) for the Voodoo kit

I was sent these pics and, full disclosure, I didn’t even study them like I should have—I was way too excited about new designs to apply basic engineering brain cells New exhaust geometry makes my brain go smooth.

My assumption is these are for the GT350, but he’s also claiming it’s a modular system that will bolt onto the GT500 with zero mods and will accept the Tri-Y setup he’s working on.

I’m going to follow up with him and see if this is real engineering wizardry or just peak CAD optimism before we all start mentally reallocating retirement funds.

 

[galaxy]

If you reach back, can you get them to expand a bit more on what he meant by modular, and the triy option?! Not having any luck visualizing that.

 

[TreeFiddyAre]

If you reach back, can you get them to expand a bit more on what he meant by modular, and the triy option?! Not having any luck visualizing that.

Yes sir !

 

[honeybadger]

I was sent these pics and, full disclosure, I didn’t even study them like I should have—I was way too excited about new designs to apply basic engineering brain cells New exhaust geometry makes my brain go smooth.

My assumption is these are for the GT350, but he’s also claiming it’s a modular system that will bolt onto the GT500 with zero mods and will accept the Tri-Y setup he’s working on.

I’m going to follow up with him and see if this is real engineering wizardry or just peak CAD optimism before we all start mentally reallocating retirement funds.

at this point, I just want you to get your hands on them so you can take pics and put them on a dyno

 

[TreeFiddyAre]

at this point, I just want you to get your hands on them so you can take pics and put them on a dyno

I second that!!! I am also going to measuring the sound level and frequency change at different rpms, inside and outside the car. Hopefully I can get the audio to replicate the change and delta in sound. In the event there is enough of change to create a measurable difference.... I think so, then she is going to the dyno for a tune prior to be force fed. Oh yeah, I will be weighing the system as well.

 

[TreeFiddyAre]

Hi guys.

This is the response to the questions at hand :

Not a problem.

Yes, the cylinder pairing that member mentioned is correct. Some of the pictures were for the Coyote.

Regarding the tri-y. There is now flanges on both sides for the secondaries. Instead of carrying the 4 secondaries all the way to the 4-1 collector, we would merge them into their own respective single pipe. It will now be an equal length 4-2-1 header.

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