Is this the SLP D/D exhaust? - LS1TECH - Camaro and Firebird Forum Discussion

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Is this the SLP D/D exhaust?

Old 12-30-2018, 03:53 PM
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Default Is this the SLP D/D exhaust?

I found this muffler on Facebook Marketplace and picked it up for $20. I thought it looked like the SLP Dual/Dual muffler but the seller said it came off a buddies 80's Camaro. I am thinking the owner of the 80's Camaro put on the SLP D/D muffler, but the guy taking it off didn't know. The seller said it was SLP, but I can't find any markings. Any idea how to tell it is a D/D?

I tried to attach photos, but I think the file size was too large. I uploaded the pics to imgur.

https://imgur.com/a/UOrIv8A
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Old 12-30-2018, 07:32 PM
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That looks like a single-in(the larger stub)/dual out (smaller 2 stubs) muffler, not a dual/dual.
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Old 12-30-2018, 09:44 PM
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Yes that is the dual dual muffler
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Old 12-30-2018, 10:43 PM
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A quick Google for "Camaro slp dual dual" looks like a match. I'd attach a pic but this site still blows on an android and it thinks "upload" means close the window.
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Old 12-30-2018, 10:51 PM
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I don't see where you guys are getting dual/dual on this muffler when there are only THREE stubs showing. A large diameter inlet on one end, and smaller outlets on each end, like a STOCK Camaro muffler. The pic is quite clear that way.
A dual/dual muffler has TWO inlets and TWO outlets. Camaro crossflows have one of each on each end, in-lines have two inlets on one end, two outlets on the other end.
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Old 12-31-2018, 08:25 AM
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The name is misleading. Personally I have no experience with it, but, my take is that its a DUAL exit muffler with DUAL tips. SLP called it the DUAL/DUAL because of that, not because the muffler is dual In dual out. Hes just asking if thats the muffler used in the dual/dual system.

For some reason I still cant upload a pic even on a computer.
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Old 12-31-2018, 10:53 AM
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I can post pictures later of my 4th Gen SLP Dual /Dual that was on my 99 TA for 18 years. It was purchased directly from SLP.

The SLP Dual /Dual has a 3 inch in from the over axle pipe. There are twin outlets one on each side. Total of three in/out holes in the muffler.

SLP Dual/Dual, that I purchased direct from SLP in 1999.


Diver side

Passenger side


Bottom side that faces road.

Let me know if you need measurements to confirm any details OP.

Last edited by 99 Black Bird T/A; 12-31-2018 at 11:08 AM.
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Old 12-31-2018, 11:55 AM
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Originally Posted by 99 Black Bird T/A View Post
I can post pictures later of my 4th Gen SLP Dual /Dual that was on my 99 TA for 18 years. It was purchased directly from SLP.

The SLP Dual /Dual has a 3 inch in from the over axle pipe. There are twin outlets one on each side. Total of three in/out holes in the muffler.

SLP Dual/Dual, that I purchased direct from SLP in 1999.


Diver side

Passenger side


Bottom side that faces road.

Let me know if you need measurements to confirm any details OP.

Whoa! Thank you so much for such a great response! How do you like the exhaust? I am beyond excited to put it on mine. I wish SLP put a marking on it or something to say which model it is, but those rivets are so unique. I have never seen a muffler with those before. Does your muffler have the Cone of Silence? Is there a way to tell from the outside of the muffler?
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Old 12-31-2018, 12:15 PM
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AH!! DUAL tailpipes into DUAL tips! Which anyone can do by the way. Dual tips?? You can get those ANYWHERE....
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Old 12-31-2018, 01:02 PM
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Originally Posted by G Atsma View Post
AH!! DUAL tailpipes into DUAL tips! Which anyone can do by the way. Dual tips?? You can get those ANYWHERE....
The tips aren't significant. The muffler was made by SLP and put on some factory cars and also available aftermarket. The muffler is one of the best flowing mufflers and also one of the quietest. The mufflers haven't been made or available for awhile now, so the only way to get them is second hand. Due to how rare and sought after they are, they are kinda expensive.

When I first got my Camaro, I got a loudmouth 2 exhaust with long tubes and an offroad Y. It was insanely loud and gave me headaches on even 30 minute drives. I have slowly been working my way to quieter mufflers.
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Old 12-31-2018, 01:06 PM
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OK, thank you for explaining this. I would bet an exhaust mfr. made them for SLP. Maybe find out who that was and see if they can put it back in production.
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Old 12-31-2018, 01:11 PM
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Whoa! Thank you so much for such a great response! How do you like the exhaust?

Happy to share TonicR6
Here are a few miscellaneous ramblings...

The SLP Dual /Dual is my favorite cat-back. Some say the D/D is too quiet, especially at idle. Some it's too quiet friends changed their minds when the TA made a few 6,800 rpm pulls and the noise ran them out of the dyno cell With long tubes, mufflex Y pipe, no cats, heads & cam the D/D was perfect for me. Quiet a idle and cruise. Local cops in my neighborhood never looked twice at the TA when it went by.

A friend's Corsa definitely sounded better at idle. He frequently criticized the D/D as too mild and cut his off his FireHawk for the Corsa. Two weeks later he was complaining the Corsa was too loud at idle and cruise. His FireHawk (bolt on no headers) Corsa was louder at idle and low rpm than my TA with HCI, LT'S, no cats & the SLP Dual/Dual.

My wife (later x-wife) has an 02 Z28 with a Flo - master. It was also louder than the TA at idle.

Back in the day that quiet idle got the TA underestimated pretty often - unless folks listened to the valve train. The Sewing machine XER cam sound was a dead give away

I am beyond excited to put it on mine. I wish SLP put a marking on it or something to say which model it is, but those rivets are so unique. I have never seen a muffler with those before. Does your muffler have the Cone of Silence? Is there a way to tell from the outside of the muffler?

I think you will like the D/D. The rivets do seem unique. I agree SLP should have stamped or etch a logo on the muffler.

The Cone of Silence aka "COS" or Ring of Silence aka "ROS" was added due to noise level restrictions. The original SLP D/D was too loud for the noise standards in place for new cars. The COS/ROS was installed in the driver side twin exhaust pipe close to the muffler. Some folks cut the pipe near the muffler and removed it.

Dual/Duals direct from SLP were exempt from the new car noise standards and didn't have the COS/ROS.

A couple of FireHawk owners noticed my TA (lid & catback at this time) was louder at idle than their FireHawk's. So the ROS definitely quieted the D/D some.

There was another SLP catback that used basically the same muffler SLP 2OTL - two on the left. I think the Cone of Silence was used in some of these. They are definitely louder. Exhaust comes in the passenger side and exits the driver side This is a sweet sounding exhaust on a 93-97 iron block LT1 fbody and really rocks on an iron block 383 LT1

FWIW - I like the SLP Dual /Dual so much I ran one down for my 91 RS it's sound is near perfect for me with the 383 LS1 it's quite for normal driving.

Gradually the TA's straight through D/D got louder as the sound deadening materials on the sides in the muffler burned out. When the TA got the 416 briefly had the D/D on the car but wasn't happy with my new Kook's Y pipe. I like the new Kook's headers. I went with a customized Hooker x pipe BlackHeart for the Kook's headers. The new set up sounds good but gets on my nerves because it's. .TOO LOUD after about half an hour.

After 20 years of LS engines, my favorite exhaust is a still a D/D for daily use and a pair of twin electric cut outs off the headers for all out.

I intend for the TA 's old D/D to go on my high mile daily driver an 02 Z28.

Last edited by 99 Black Bird T/A; 12-31-2018 at 01:20 PM.
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Old 12-31-2018, 01:23 PM
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BTW back in 1999, folks cut SLP Dual /Dual off left and right and $100 would often buy an almost new D/D.
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Old 12-31-2018, 02:31 PM
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Originally Posted by G Atsma View Post
OK, thank you for explaining this. I would bet an exhaust mfr. made them for SLP. Maybe find out who that was and see if they can put it back in production.
To be honest I think a magnaflow or TSP is a better option now. Not sure if the SLP system was all stainless or not, but I dont see it flowing significantly better then a magnaflow or TSP, or even GMMG. Not sure what the fuss is about over really wanting one. For $20 Id take it though. Looking at factory pics the over the axle pipe is crushed to give clearance like a factory y pipe.
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Old 12-31-2018, 02:34 PM
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Originally Posted by 99 Black Bird T/A View Post
BTW back in 1999, folks cut SLP Dual /Dual off left and right and $100 would often buy an almost new D/D.
True...
Back in 2007, I was lucky enough to find a NOS dual/dual muffler and tailpipes (minus the tips) right here on LS1tech...


Believe it or not, the $250 Jeg's catback on my current car sounds a LOT like it IMO...


WOT run with the SLP dual/dual (10 years ago):


And WOT run with the Jeg's catback (few months ago):




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Old 12-31-2018, 03:23 PM
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if you'd like i can look in an old SLP catalog and text you what the dual dual looked like just pm me thx.
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Old 12-31-2018, 04:22 PM
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They ARE very similar! I actually give Jeg's the edge but don't know how it is on the road. Is the SLP a packing-type or baffle, or both?
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Old 12-31-2018, 05:33 PM
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Originally Posted by G Atsma View Post
They ARE very similar! I actually give Jeg's the edge but don't know how it is on the road. Is the SLP a packing-type or baffle, or both?
I "think" the old dual/dual was both.
I only chose the Jegs because I had removed the rear mount turbo setup, and needed something inexpensive.

Was pleasantly surprised when I fired the car up that first time. Very quiet at cruise, but decently loud at WOT.
I just added a cutout for the times I want loudER. Lol.

BTW, back 10 years ago, everyone swore that a cutout would shave a tenth or two off ET, but mine ran identical with it open or closed.
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Old 12-31-2018, 06:06 PM
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Originally Posted by rel3rd View Post
BTW, back 10 years ago, everyone swore that a cutout would shave a tenth or two off ET, but mine ran identical with it open or closed.
Shows how good the full system was!
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Old 12-31-2018, 07:09 PM
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Originally Posted by G Atsma View Post
Shows how good the full system was!
No doubt! FWIW, my Jegs catback evidently is right there too...as in no gains with cutout open...well, except for being louder, lol.
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