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Discussion Starter #1 (Edited)
Many years ago I had removed the rear silencer, which kept rusting out, and replaced it with a pipe I had made at the local exhaust shop. To me it sounds much better than the 2 box setup. I showed it to Center Line when I was picking up other parts. Soon after they started selling their "stinger". Coincidence? I think not.

This weekend I removed the 1989 factory exhaust manifold and 1 piece, 2 into 1/cat. I replaced them with headers my sweetheart gave me for Christmas and a Magna Flow cat for an 81 spider.

The new set up is louder which I do not really understand. I may put the 2nd box back on.

For anyone who wishes to do this I have a few notes.

1) It's a pain in the butt. Not for the faint of heart.

2) Don't buy the powder coated version. It burns off immediately. Spring for the chrome or ceramic.

3) You will need to cut about 2 inches off the two header tubes to fit with the '81 cat.

4) Cut four 3/4 inch slits in each of the two header tubes. This will make it much easier to install the 2 -1 fitting.

Note: Once you have installed the 2 into 1 on the headers you won't be able to remove the header without removing the engine.

4) If you can find a three hole flange to match the cat, buy it. Otherwise, cut the flange off the old cat and grind out the pipe until it fits on the 2 - 1 adapter. This takes time because the steel has been hardened by multiple heat cycles.

5) After cutting the header tubes to length, bolt the headers to the head with new copper gaskets in place. You may need to jack the engine up a little to feed the two piece header into place.

6) Install the cat to the muffler. There is an arrow telling you which way it goes. There is a small input tube on the 81 cat that you will need to plug. I used an acorn nut.

7) Slip the flange onto the 2 -1. Don't weld it yet. The connections are not straight,

8) Pound the 2 -1 onto the headers until you can just barely fit the tube up to the cat..

9) Put the bolts through both flanges and tighten them up. This will pull the flange up to the cat flange. Tack weld the flange in place.

10) Remove the Cat completely.

11) Finish welding the flange to the 2 - 1.

12) Grind down the pipe protruding the flange until it is flush.

13) Grind down your embarrassingly ugly welds. (That may just be me.)

14) Re-install cat with gaskets.

You are now done. (Except for reassembling the air intake, cleaning up all the tools, bandaging the spots where you hit your hand with the grinder, etc.)
 

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The middle box is a resonator, not a muffler. The rear box is a muffler. The front box, the cat converter works as a muffler. You can replace the rear muffler with a stinger and your car will not be too loud if you have a cat converter but it will be obnoxious if you do not have a cat. My current setup is no cat, a Borla straight through muffler in the middle and a straight pipe at the rear. It sounds great. you can hear it at
 

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That sounds nice when you are "on it" !!

What about when you are just cruising along, does it drone ?

I've messed with a few exhaust combinations, trying to get a sound like you have, but the droning at cruse made me take them off and go back to stock.
 

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There is a drone from about 2800 to 3200 rpm. It seems louder with the top up.
 

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Discussion Starter #7
MIDDLE BOX

The middle box is a resonator, not a muffler. The rear box is a muffler. The front box, the cat converter works as a muffler. You can replace the rear muffler with a stinger and your car will not be too loud if you have a cat converter but it will be obnoxious if you do not have a cat. My current setup is no cat, a Borla straight through muffler in the middle and a straight pipe at the rear. It sounds great. you can hear it at https://www.youtube.com/watch?v=Azr0mBTDJl4&feature=youtu.be
I replaced the cat with a magnaflow low restriction. It may not be giving the muffler effect of the factory unit. The sound is "rattley" from 2500 - 3000 rpm. What is the dif between the factory resonator and the Borla middle muffler? Herb
 

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The Borla is straight thru. You look into one pipe and see out of the other one. Not much restriction!
 

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Discussion Starter #9
Tuning the exhaust note

The Borla is straight thru. You look into one pipe and see out of the other one. Not much restriction!
My middle box (resonator) is original to the car. (I've had the car since new and never replaced it.) For all I know the whole inside has rusted out.

Now that I have headers and the Magna Flow cat, do you think the Borla version of the middle box would cut down the raspy, rattling sound? It's irritating.

Is the Borla middle box a true muffler or just a replacement resonator?

Herb
 

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It's a muffler. It is reasonably quiet if you are light on the gas pedal. It is a lot better than the resonator/stinger combo that I ran for a short time. I would have irritated my neighbors if I had kept that.

Here is the unedited version of the final test run in the Spider where you can get a better impression of how it sounds when it is not wide open
 

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This weekend I removed the 1989 factory exhaust manifold and 1 piece, 2 into 1/cat. I replaced them with headers my sweetheart gave me for Christmas and a Magna Flow cat for an 81 spider.

Just out of curiosity, I'm wondering why you kept the cat. That sounds like a lot of trouble just to fit a cat on a 26 year old car. Is there a Colo. law that requires a car that old to retain a cat? Normally, those CSC headers (assuming that what they are) are pretty much a bolt on operation with a stock (i.e., non cat) exhaust system.
 

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Aftermarket exhaust has a reputation for needing much massaging to get to fit; especially headers. You may get lucky, and the welder was accurate that day, but not usually. Even the stock Magnaflow exhaust I put on my 86 needed the transmission hanger cut off and relocated, as it was way off.
 

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Alfaparticle, which borla is it? Sportsman round or oval?
It is a Borla PRO-XS - about $80 from Summit Racing
 

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Aftermarket exhaust has a reputation for needing much massaging to get to fit; especially headers.
I've had marginally better luck and the new Centerline headers (made by CSC) supposedly fit better than the stuff sold back in the day. I bit the bullet and installed an Alfaholics system from headers to tailpipe on my Super. It's the first aftermarket system that fit perfectly. It sounds great too. The Banks boys do good work.
 
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