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Old 10-09-2013, 02:45 PM   #1
Join Date: Aug 2013
Vehicle: 2005 Mustang GT
Location: Texas
Posts: 29
Question SLP Loudmouths--Bad Choice?? Also, route to take in order to install cats with setup?

Well...after much consideration on what type of axleback exhaust to get, I ended up going with the SLP loudmouth. Problem is, is that I have LT headers w/ an o/r x-pipe (I bought the car like that and it used to have the Flowmaster American Thunder axleback). Not to mention it is LOUD. Big mistake? Any of you think this would be too obnoxious or know anyone with this set-up? I have mixed-feelings about it. I like the start-up sound and everything, but I'm starting to think that it is just too much without the cats. So, I'm really considering on getting cats to lessen the screamy Loudmouths (not that I don't like them, I just don't want them to be obnoxious).

Another thing/problem: I went to a local exhaust shop, asked them to give me a quote to install cats. Welp, they looked under the car and told me I've got NO room to just install cats. So, they advised me if I wanted them, I would have to get shorty headers, and then they could do the work. (I'd also have to buy a regular mid-pipe too). All in all, I'm lookin around $2500 b/c they'd have to take out the motor for install and said the cats would run me about $400/cat. Ridiculous, huh?

MY question: Can't I just order a "catted" shorty-mid-pipe? 1. Are those equipped with actual catalytic convt's or are they just made for fitment if you HAVE cats?

Oh, and one MAJOR problem: Since I bought the car w/ the lt's, I honestly can't find any stamps on the pipe to determine what brand they are. So unless I know, there's no way I can just order any catted shorty-mid-pipe.

Suggestions, thoughts, or advice? I'd GREATLY appreciate it!!

btw--I like the slp's, but if I can get cats for a reasonable price, that'd be great.

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Old 10-09-2013, 08:36 PM   #2
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I ran longtubes with an offroad pipe and Mac Boomtubes, which are essentially the same thing as Loudmouths. It was too loud and I changed to Bassani. Are your longtubes actual longtubes or more a midlength? These: http://www.americanmuscle.com/mac-ch...be-0509gt.html. or these: http://www.americanmuscle.com/jba-lo...rs-0509gt.html.

If they’re more like the MAC’s you can definitely put cats on your current pipe (and I happen to have a brand new set of SLP high flow cats for sale). Just cut the straight pipe after the header collector and weld/clamp it in.

If they’re like the JBA’s, then you’re going to have to push them back and would need some really low profile cats. Additionally, that far back the cats may not get hot enough to work properly (not sure of exhaust temps past the transmission). While difficult, I can tell you that you do not have to pull the engine to change headers. More like lift it 3-4” and that’s good enough. No way all that work should cost you $2,500. I had my full O/R LT exhaust, among other work done for $450.

To quiet it, you could look in to different mufflers (which should also reduce the drone) or adding resonators before the axle.
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Old 10-09-2013, 08:44 PM   #3
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I ran LTs, O/R h-pipe, and muffler deletes for a month before I couldnt take it anymore and put the stock manifolds and h-pipe back on. I could be heard almost a mile away when keeping it under 2k rpm and almost 4 miles away at wot shifting at 5200 rpms

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Old 10-10-2013, 12:21 PM   #4
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Vehicle: 2005 Mustang GT
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Did you honestly expect what is essentially a resonated exhaust tip to do very much muffling?

Cats will make some difference but not that much. If you want quieter just get a different axle back.

Also if you can post a couple pictures as best you can of what the headers look like, and whether they are plain steel, stainless, or chrome, someone can probably identify them.
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Last edited by ghunt; 10-10-2013 at 12:23 PM.
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Old 10-11-2013, 08:14 AM   #5
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Skip the cats and get some M80s welded in before the axles. I run catless midpipe with my longtubes, my Bassani Race mufflers are just a resonated pipe so they were LOUD and farty. Did the M80s and sooooo smooth but sounds mean as hell when I get on it. No drone.

M80s were $44 a piece (got them from Jegs, AM usually is out of stock) with $90 install that took 30 minutes. So worth it.

Oh and for the stamp, most brands have a tag welded on the pipes a few inches from the heads.
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Old 10-11-2013, 12:57 PM   #6
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I think resonators like that help with the quality of the exhaust tone but not so much the volume. My Magnaflows are basically identical to the M80's, which have about an inch of packing around the pipe. That's really not enough packing to do much. I installed mine so it wouldn't be stupid loud, but it's still really loud at anything above 2000 RPM really.
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Old 10-11-2013, 12:57 PM
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