Undercar Exhaust

[Vspeeds]

A few people have asked me about my undercar exhaust; How I did it and how it sounds. So here is how I did it. I have the 289 USRRC kit and wanted the exhaust to exit in front of the rear tires. I have a stroked 351W producing over 500 HP. I chose the SpinTech 7000 Cruiser muffler as it is a low profile muffler, 2¼” X 9” X 16” in size, with 3" oval inlets and outlets. From the engine I used the BBK "shortie" headers. I used half of the kit supplied "J-Pipe" with the end with the flange connected to the headers. The other end of the J pipe was cut off and welded to the SpinTech transition tube, 2 1/2" round to 3" oval. Then the oval tube goes into the muffler. Then after the muffler, a 90 degree horizontal elbow was used toward the exhaust tip. The elbow was cut to get the angle which I thought looked good. With the round tubes of the frame sitting at 4-1/2 inches front and 5" rear above the ground and with 15 inch wheels (235/60-15 front tires, 255/60-15 rear tires) I only scraped once in over 6000 miles of driving and that was with me driving too fast over a series of speed bumps in the Costco parking lot. It was also Cerakoted in the Titanium color.

Here are some photos as well as a video. In the video, I tried to get the cruising sound at 55mph and then accelerated. I did not mash the pedal as I have skinnier tires (compared to the MK4 427 kit) and I have no roll bar. Rather it was a more of an easy aggressive acceleration. This car has plenty of power and torque and I think it sounds good for my style of car.


YouTube Video:
https://youtu.be/66WlM4vrr94




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[JohnK]

Beautiful car! The overall aesthetic with the luggage rack and no side pipes is fabulous. It's a very different, and more understated look.

[Vspeeds]

Beautiful car! The overall aesthetic with the luggage rack and no side pipes is fabulous. It's a very different, and more understated look.

Thanks. Thats exactly the look I was going for. A vintage British sports car of the era

[Vspeeds]

Beautiful car! The overall aesthetic with the luggage rack and no side pipes is fabulous. It's a very different, and more understated look.

And I plan on using the luggage rack when this Pandemic cools down. I have a lot of travel adventures planned. This car has turned into my daily driver. I have over 5000 plus miles since January and I even commute to work in it.

https://youtu.be/OqGFOCcwRg8

[KDubU]

Definitely a stunning roadster. Love the colour but I am bias to blue/silver shades. How is the db level with the pipes like that? Got to be a bit less loud and it’s one idea I have been toying with for a new build as my wife felt my previous was too loud.

[Vspeeds]

Definitely a stunning roadster. Love the colour but I am bias to blue/silver shades. How is the db level with the pipes like that? Got to be a bit less loud and it’s one idea I have been toying with for a new build as my wife felt my previous was too loud.

Good question Kyle

I'm not sure how accurate my iPhone decibel app is but it read around 53 decibels in ambient background noise. Around 106 decibels at idle. And 120 plus revving the engine. This is a lot louder than I thought. However, to me, it doesn't sound as ear piercing as other Cobra's I've heard. Maybe its just the tone of my mufflers...But then again I'm half deaf to begin with.

YouTube video:

https://youtu.be/beEhrU10cJM

[2FAST4U]

I have something very similar. Had a custom header shop make the headers and n to the mufflers. I did the rest
https://thumbs2.imgbox.com/66/03/FNJzPt2y_t.jpeg (http://imgbox.com/FNJzPt2y)

https://thumbs2.imgbox.com/37/14/bXBR4Nlz_t.jpeg (http://imgbox.com/bXBR4Nlz)

https://thumbs2.imgbox.com/b3/89/LoHebUTJ_t.jpeg (http://imgbox.com/LoHebUTJ)

https://thumbs2.imgbox.com/97/c1/5jPVeEBJ_t.jpeg (http://imgbox.com/5jPVeEBJ)

[GTBradley]

Nice work. I really like the British look and struggled with doing the same or the 427. The luggage rack will make a big difference when traveling I think. With a handle like Vspeeds I thought the office would be a cockpit, but now I’m thinking you’re a professional video editor.

[KDubU]

Thanks for the vid and db reading. Interesting as I would thought it would be a bit lower but then again to me it sounds great.

PS, I am half deaf too and I think my wife is concerned I would lose the other ear with these cars.

[Vspeeds]

Nice work. I really like the British look and struggled with doing the same or the 427. The luggage rack will make a big difference when traveling I think. With a handle like Vspeeds I thought the office would be a cockpit, but now I’m thinking you’re a professional video editor.

Thats funny. 30 plus years ago, before marriage, kids, and a career change, the office was a cockpit...and the video editor; I began making team sports videos for the kids’ and just enjoy learning and making videos for fun. I’m just a lowly ol civil servant.

[GTBradley]

Thats funny. 30 plus years ago, before marriage, kids, and a career change, the office was a cockpit...and the video editor; I began making team sports videos for the kids’ and just enjoy learning and making videos for fun. I’m just a lowly ol civil servant.
Me too. Up until two years ago I called the cockpit my corner office with a view (and that’s what I miss most about it) but now I produce aviation charts for the government. Considering the current prospects for airline pilots I feel pretty fortunate to be working from home. I never thought a 100 mile long commute to work could be fun but you sure made it that way. Can I ask what software you used for the video editing?

BTW, “lowly ol civil servants” make the world go round.

[ChopperJustin]

I have a question for you and others who've gone with/contemplated the under-car exhaust. Have any of you considered rear tail-pipes like many of the period street Cobras had? I've heard many with IRS say it's not possible, or there is no room, but what about those with either the 3-link, or 4-link rear end? It looks like the lower connecting rod might be in the way...

I'd love to build an exhaust similar to this but throw some polished pipes out the back - just not sure if the clearance is there.

Thanks - Justin128591128592

[Vspeeds]

I have a question for you and others who've gone with/contemplated the under-car exhaust. Have any of you considered rear tail-pipes like many of the period street Cobras had? I've heard many with IRS say it's not possible, or there is no room, but what about those with either the 3-link, or 4-link rear end? It looks like the lower connecting rod might be in the way...

I'd love to build an exhaust similar to this but throw some polished pipes out the back - just not sure if the clearance is there.

Thanks - Justin128591128592

Justin
I have the 3 link. Although I love the rear exhaust, I did not even consider the rear exit exhaust as the 3 inch pipe wouldve been too large to bend up and fit. Even with a smaller diameter pipe I dont think there is enough adequate room in the wheel wells to do it without having to chop things up. If you really want to do it I’m sure there is a way.

[Vspeeds]

Me too. Up until two years ago I called the cockpit my corner office with a view (and that’s what I miss most about it) but now I produce aviation charts for the government. Considering the current prospects for airline pilots I feel pretty fortunate to be working from home. I never thought a 100 mile long commute to work could be fun but you sure made it that way. Can I ask what software you used for the video editing?

BTW, “lowly ol civil servants” make the world go round.

For the video editing; I have Apple products so I go back and forth using the free app called iMovie for simple edits and the paid app Final Cut Pro

[Cutter 54]

Very nicely done. Looks very clean. I am also considering this. It reminds me of the Slab Side Cobra. Before I saw your post I noticed the one below, which looks similar EXCEPT for the rear exit. This might also allow more muffling or resonator mods to keep noise down. Do you, or anyone else recognize this post or its author?? The link to how he did the mod doesn't exist anymore. It's pretty old. Maybe Dave L (FFR) can track it down. I'd like to see jolson42's work.. Thanks.


jolsen42
Charter Member
Joined Jun 23, 2002
1,604 Posts
#7 • Oct 10, 2014
Here is how that I did mine.

John O

Under Car Exhaust for Factory Five Roadster - FFR FAQ

[mark jones]

also looking for a way to run pipes out the back or keep the roar to a minimum. Any ideas would be great

[ScottR]

Did you have any fitment issues with the BBK headers? I've read elsewhere that the rear pipe on the driver's side hits the footbox.