My 3" spintech muffler came in today, so tomorrow I'll be starting my exhaust swap.

First of all, here are the engine specs:
355 cubic inch
Forged flat top slugs
461 fuelie heads
Compression around 10:1
Summit hydraulic flat tappet cam, 214/224 .442/.465 112lsa
MAF TPI with SLP runners, accel base, holley 52mm tb, 24lb injectors, AFPR, etc.
Hedman 1 5/8" headers, heddman 2.5" y-pipe
3" dynomax cat
T5 trans

I want a new exhaust because the current dynomax is too quiet, and I feel that the 2.5" crossflow muffler is effecting my flow, although probably not much. However, this winter I'm planning to upgrade to SPDC vortec heads, vortec HSR, Lunati voodoo cam, and hopefully new headers with a 3" y-pipe.

Currently I've got a dynomax 2.5" "super turbo" catback. I had my fiance take 3 video clips tonight in the dark so that I can provide a comparison between the old and the new.

I have 3 clips:
1. Driving by
2. Backing into the driveway
3. Idling, revving to 3,500 rpm.

The dynomax clips will be uploaded tomorrow morning from work (I have dial up at home ). I think the dynomax sounds great, but it's WAY too quiet. Even when I'm on it, it sounds virtually stock. What I do like about it is that it's got a very deep rumble to it. You can hear it in the video clips, although I think the camera mic is very bass-heavy, because it doesn't sound that bottom-heavy in person. Like I said, imagine stock but deeper.

The new catback is comprised of the dynomax 3" intermediate, dynomax 3" over-axle pipe, the spintech muffler, and some 90* and 45* pipe for making a tail pipe.

After I finish the swap, I'll be writing a tech article for iroczone.com, and I'll post that here too.

 

Here are the 3 sound files:
Driving by: http://www.iroczone.com/technical/Exhaust/Dynomax1.AVI
Backing up: http://www.iroczone.com/technical/Exhaust/Dynomax2.AVI
Starting & revving to 3500: http://www.iroczone.com/technical/Exhaust/Dynomax3.AVI

To get an accurate idea of how this sounds, don't turn it up so loud that the background noise is audible. If you crank the volume, the exhaust sounds pretty good, but no longer realistic.

 

wow that dose sound stock

 

I got everything put on today. Right now I've got a straight pipe on until I get the old exhaust pipe out of my slip-on cat.

I need a couple more clamps before I put the car down, but I started it up in the garage. Holy hell it's loud.

I hope it's a lot quieter outside. Either way, this setup should definately flow better than the old 2.5" dynomax crossflow muffler.

 

I can't wait to hear that catted spintech setup!

 

I wish I knew how to record the sound of my muffler.

Because I have a Dynomax as well, different though, a Thrush Magnum, ending with a turndown pipe before the rear end.

That deep sound may just be real Dynomax typical

 

Spintech is on, and since I have a piece of reducer pipe stuck in my cat, I'm running a testpipe until I get my cat issue straightened out.

Right now I'm really not really too impressed with the sound. At idle it has a nice sound similar to the other spintech clips I've heard here, but at higher rpms it's just nasty, like a Winnebago with a hole in the muffler.

Interior has no resonance, which is nice, and when I'm just cruising along under 2k rpm it's not too loud to interfere with my radio, but when I step on it, it gets raspy and unpleasant.

I'm hoping that when I get the cat on a lot of that nastyness will go away, but if it doesn't, I'm finding a new muffler.

I'll get sound clips as soon as I can, but if I rev it to 3500 in my driveway like I did with the dynomax, I'll probably have a bunch of pissed off neighbors.

 

I knew it would sound REALLY raspy without a cat. My flowmaster was bad at 2000-3000rpm without a cat. It sounded like a hillbilly pickup truck. Once I installed the Maganflow High-flo cat it went away..

 

That's encouraging. I just had high hopes that this would sound better, because every old muscle car I hear without a cat always sounds fantastic.

The other thing that disappointed me was just how noticable the sound is on a single-exit vs. a crossflow with pipes on both sides. I hear the entire exhaust through the driver's window now instead of the balanced sound I had before. That's going to take some getting used to.

 

Here are the sound clips with the Spintechs:

Spintech1: Driving by the house, but a little easier because there were people around.
Spintech2: Backing into the yard
Spintech3: Startup, rev to 3500, 4k, then idle at 750.
Spintech4: Backing into the yard again.

One thing about the clips... this $200 digital camera that we made them with seems to make all exhausts sound the same. In the videos, this new exhaust sounds similar to my dynomax, where in person, they are drastically different. The Dynomax has a very deep tone, but is very quiet, even under hard accel. The Spintech is very loud and has a much wider range of frequencies, and is very raspy under hard acceleration. While cruising and driving easily, it's docile enough that you can still hear the radio and carry on conversation.

I drove the car around a little bit more last night and I'm starting to get used to the sound.

 

those spintech clips above have a cat?

 

No, I haven't put it on yet because I've got a piece of the old exhaust pipe stuck in it.

Hopefully I'll have the cat on this weekend.

 

Jim, you have a reverse light out.


Car dosen't sound bad. I'm sure a cat will clean up the sound a bit.

 

It sure sounds more like a gurgle than the Dynomax did.

I had probably the same cat-back you did and I loved it. It wasn't that loud at idle either, but it sure sounded good when I tromped on it. And that was just a 305 TBI.

But I also had 3.5" rolled end, 15* angle 18" long tips on mine to. That really woke it up. Plus a high flow Catco (spelling) cat.

That spintech would be easy for me to get used to, as long as it was on someone elses car. Just my 2¢.

I hope the cat helps.

 

Did you manage to get the converter on Jim?

 

No. I just moved into a new house, so until all that crap gets sorted out, the car sits in the garage. I haven't even had time to get the piece of pipe unstuck from the cat yet.

 

cat will definately tone down the exhaust note completely.

 

nice. i love my spintech too except i have a cat on mine. here is a clip YouTube - 1990 iroc vert

 

how did you go from a 2.5 to a 3 inch? I want a new cat back bad.

Its way to quiet with headers!!

 

Was the old one that you changed the 17739 super turbo cross flow muffler?

Did you notice an improvement in power when you swapped it out? Always hard to tell on a sound clip but I thought it sounded pretty good.

 

I took off the 2.5" stuff and installed 3" in it's place.

 

I'm not sure what the part number on the old one was. It was the 2.5" Super Turbo crossflow.

I didn't really notice an improvement in power, but I really didn't expect to. I did run 2 tenths faster with another 1 or 2 mph at the track, but I can't really say that the exhaust gets all that credit. It was cooler than during previous runs, and I also cut significantly better 60's.

 

Smart move.. i really liked my dynomax catback. Till i found out what a piece of crap the muffler was for a larger motor.

 

Jim.....................If I understand correctly you believe that the 2.5" Dynomax system was not restricting your 350 cu in motor much if any.

Just wondering as I have full exh now but it's just too loud not having a cat installed. Also mine is only a 305 at this time. Would changing the 3"in/out Flowmaster for the crossflow quiet it down without restricting?

Thanks.........DM


Edit: After considering the above posts that stated after installing a cat the noise would improve I thought I'd give it a shot. I already had a Dynomax 3" Bullit so I installed it where the cat would reside. Mucho nicer. Wished I had done it long ago.

Thanks guys as you shook some grey matter loose.