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Are these THE side pipe mufflers to get? Flowmaster 13530320 Slimeline

39K views 122 replies 39 participants last post by  conger 
#1 · (Edited)
(re-posting from my build thread)

I had been looking for side pipe mufflers for some time. The noise level has always been an issue for me. I wasnt willing to spend the $$ on mufflers and then have the packing blow out and have to go through the process of cutting out the glass pack and starting over again. The plan was to go with a rebuildable muffler. The only one I was aware of, was made by Burns Stainless, but the pair of mufflers ranges from $900-1200. I had a friend with them and they worked incredibly well... and rebuilding was easy enough from what I found. The price was keeping me from making the jump. I had even considered making mine rebuildable.

I was literally a day away from spending $1200 on rebuild-able Burns Stainless mufflers when I found the new Flowmaster 13530320 Slimeline. We heard about them at SEMA a few years ago, but no one at the booth knew anything about them. Searching their web site netted nothing as well. Before making that last call to Burns, I decided to do one more search and found a few discussions online, including here along with a part number. Tennessee Tim installed them and it appeared he was pretty happy. With that, I was ready to take a chance on them.

https://www.youtube.com/watch?v=Xuww8Yjyzsk

https://www.youtube.com/watch?v=HlDiQkWNhIY

They are SS, have no packing to burn out and have a lifetime warranty and at $209 each they are fairly priced. From what I gathered they are very effective at taking the sharp tone out of the exhaust which is what we need. I had to wear ear plugs with the FFR pipes, and even then my ears rang after driving the car.

They have an added benefit of having a special insulation that really cuts down on the heat of the outer shell. Anyone that has had a "cobra bite" and the resulting lifetime scar understand the importance of this.

So on with the install:

Made up a support to get the new mufflers in the exact spot desired.



After welding them up. It was a bit tough as the fit-up wasnt as tight as one would prefer.







Ive had the oppty to put maybe 300 miles on the car since installing the new mufflers and Im really happy with the change. As mentioned before, earplugs were a must, and even then my ears were sore. After the new mufflers, I havent worn them and my ears dont hurt :D The sound is just perfect to me. Still sounds like a cobra but without the sharpness.

Against my better judgement, after coming back from a spirited drive I decided to try to quickly touch a pipe where your leg would contact it. First quick tap... wow, no skin left on the pipe... tried a bit longer, then longer still... and no burn. Yes its still hot and I dont know if I could leave my hand on it for more than a second, but its cool enough for your brain to register and tell your leg to move it before getting a 2nd degree burn. This alone is worth the price of entry.

The only drawback to these pipes is they are fairly heavy. If you are really concerned with weight, then the Burns are probably a better bet.

Overall, I couldn't be happier and I have several friends that are buying them as well once they heard them on my car.

Appearance wise, I think they look much much better than the normal sized glass pack. I was a bit worried that they would be to big looking, but after installing them, I like the looks better.

David
 
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#93 ·
I have been following this thread and purchased the Flowmasters. The FFR pipes are fun when the car is first driven but then got on my nerves for a longer trip. Like some others I got one of each weld type and the one done with TIG had the inlet sticker. The one done with a MIG took quite a effort to grind out the weld for the 3.5" pipe to fit into. But was it was done and they were welded into the FFR stainless ones. Thank you David for finding the Flowmasters and posting this thread. They are everything you said and I like them. I'm thinking of adding a radio now that it can be heard and conversations can be had at highway speeds.

I kept the heat shields because my wife got a cobra bit before they were installed and is now twice shy. The mufflers themselves run much cooler but the tip is still too hot for bare skin.
 

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#94 ·
Anybody put these on a Dyno yet?

Jeff
 
#96 ·
Thanks Bobl! Much appreciated. Contemplating these for my coupe. The stock ffr pipes are super raspy and loud. This might be the answer for me.

jeff
 
#97 · (Edited)
Has anyone put a wideband O2 bung in? I have one in my passenger side collector. Looking at the pictures, there is not much of it left.

Is there any consistency as to where the nicer welded ones came from? Or is it the usual case of the older ones were a little nicer?
 
#98 ·
Not quite sure of your question about the 02 bung placement. What pictures are you talking about?

None the less, sensor placement is important. They should be between 15 and 75 degrees from horizontal and should not be too far from the closest exhaust valve or special precautions or solutions should be taken. The angle avoids getting contaminates in the sensor like water from condensation and combustion. The distance from the exhaust valve has to do with keeping the sensor warm enough to read properly and there are solutions to get the proper reading.

Do you only have one on the passenger side? There should be one for each bank of cylinders.

Here is a good six page description of 02 sensor placement:
http://wbo2.com/lsu/LsuInstal.pdf

This is a shorter version of the above pdf:
Oxygen Sensor Installation Issues (Tech Edge)

One other note not related to the last post. I read the other day that these mufflers have a longitudinal seam which shows up once polished so position the muffler so the seam is hidden against the car body when welding them up or tacking them for later welding.

George
 
#99 ·
George,

Thanks for the info, but I have a wide band for carb tuning, not a narrow band for EFI. Wide band needs to be away from the high heat that a narrow needs, so they are normally in the collector. Only 1 is really needed for carb tuning and is only in the pipe while tuning. It is pretty much impossible to get the correct angle in the side pipe, but since they don't stay in permanently, it is not an issue.

The pictures in this thread show that with the 30" muffler, there basically is no straight piece of collector left ahead of the muffler. I would imagine that I could still get it in just before the muffler, but would like to see a pic if someone already has it figured out.

I will definitely make sure that I have the seam in a hidden position.

I would do the 24" ones, but I need all the noise reduction I can get.
 
#100 ·
There's plenty of room for the 02 sensor. Just leave as much collector as possible when you cut the old mufflers off. The collector slides inside the Slimline. Insert it just far enough to get a good weld.

Bob
 
#102 ·
I have my mufflers. It doesn't look like it will be a big deal to make some kind of a jig for the welder. Looking at my FFR ones the passenger outlet is a little crooked anyway. So I should end up with straighter pipes than what I have.

Opinions on the turnouts please. Straight out like FFR does? I like the look. Does angling them down really make any noticeable difference? How many degrees if you did?
 
#103 ·
Avalanche325: I had planned to modify my sidepipes by turning the "turnout" approximately 30* down, but one of the local Cobra owners warned that doing so will result in the exhaust pulses kicking up a lot of road dust. So I decided against the turn down.
 
#108 ·
Good point! I already do a pretty good job of keeping my street clean as it is.

I looked EVERYWHERE for a price better than $216.00 ea. I searched on Amazon with the part number and came up with a listing at $188. When I put it into my cart, it was $216. So, I went with Summit because I like their customer service and return policy. If someone sees something better, please post it. Summit will price match in the next 30 days.
 
#105 ·
Well well..... I just put mine up for sale in the classifieds. 300+shipping
 
#109 ·
anyone use the 24"? i want to keep my Drummer Mike shields.....i know they are not needed with these but i love their look...and i think the 30s will look wrong.
 
#110 ·
I have Drummer Mike shields on 30" Slimlines and they look fine. I had to buy larger t-clamps.
 
#111 ·
I am doing 30" as I need all of the quiet I can get with my somewhat radical cam. I have been to meetings with 30 Cobras and mine was easily the loudest. 24" would probably be fine if yours isn't that loud to start with. If I wasn't soooo loud, I would think about 24" also for the look. The other advantage of the 30" is that more of the pipe will be cooler. I think it will be one of those things that I won't notice after a week, just like the mufflers being larger diameter. I will hopefully notice that my ears don't ring even with earplugs.

If you look at pictures of originals, the FFR pipes are a little short. Most of the shots that I found, they go back to where the hip meets that body behind the door. Which for my eye, it the ideal place aesthetically. Measuring, that adds about 3 inches to the overall length. That will be easy with the 24", and not too bad with 30". There is just not a whole lot of 3 1/2" pipe at either end.

Here is my plan. Let me know if you see any issues.

Leave 1" of the straight pipe after the collector. I like the look and I can put my O2 bung in there. The turnout will be 7 3/4" long. This is just a little past where it completely straightens out. This will put the very back of the outlet right at the join line of hip and body. I am going to keep the junctions straight in both planes. I am leveled fine with the FFR pipes which are straight horizontally, so don't need to fudge any angles. I am going to keep the 90* angle for the turnouts.

How much pipe should I leave to go into the muffler? I am thinking not much at all like 1/4"?
 
#112 ·
The muffler slides over the 3 1/2 inch collector, so leave it as long as possible. You can position the muffler where you want it and tack weld into place. You can also shorten the turnout some. I just finished my first real ride in my car. Drove it 100 miles. The exhaust noise didn't bother me at all. No roaring or ringing.

Bob
 

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#113 ·
I finally did it! There was a LOT of polishing, caught a nasty mult-week cold, Christmas, etc. I took out all of the manufacturing marks like from the rollers, jigs, etc. Then started sanding and buffed with a kit from Cadwell that a friend loaned me hooked up to my trusty HF buffer. It did a great job. Then found a local tuner / turbo place to do the TIG welding. Including the mufflers, stress relief pads, hanger tabs, and an O2 bung, they charged me $106, for some impressive looking welds. What a deal!

I have claimed to have the loudest Cobra around. I have been in groups of 20-30 at a time, and my car was easily the loudest. I had to wear earplugs even on a ten minute drive. I was a little worried that all of the effort would not yield enough results. When I fired it up, I was shocked. No more top fuel Cobra. Now it has a deep aggressive rumble. The higher harsh biting tones are gone. My wife and I went for a 15 minute ride and we could talk. We used to have to yell at each other, most of which was "WHAT??". It will still get plenty loud at full throttle, so it's still all Cobra. I think this is going to make my car a lot more enjoyable overall.

Crazy at it is, we both touched the mufflers when we got back. We were able to put our hands on for about a second, and I'm a wimp with heat. That would have left skin on the stock mufflers and life-long scars. You won't pull over and sit on them and eat a sandwich or anything, but you will be able to get away in time if you touch them with your leg. One scar for me is enough.

I was a little baffled how you could quiet it down so much and not lose power until I cut the old mufflers out. The FFR mufflers have 2-1/2" inlet and outlet. The Flowmasters are 3-1/2".

I want to thank you guys that went before me and special thanks to bobl for the testing.
 
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#114 ·
I've put over 5,000 miles on mine with the 30" flowmasters last summer. 2400 miles of that driving to FFR open house for s weekend dash. Never a complaint! My partner on the drive built a set for his car after the drive!
Love that sound!
 
#115 ·
Old thread, even older questions (lol)

I have the stock FFR pipes that are polished stainless steel and very purdy. They are loud, of course, but also have a sort of hammering sound (not like a baffle is rattling, just the pitch), especially on deceleration, that I'm not crazy about. I'd love to quiet them down a bit and deepen the tone. I love the look of them so I'd rather work with these if possible. The Cobra only has 1,600 miles but is 7 years old.

Did these exhausts come with fiberglass inside that maybe has settled or worn? And if I wanted to rebuild or even replace them, how does one go about "replacing" the muffler? Do you cut the welds before and after that center section, weld back in the new muffler, have it ceramic coated and then reinstall the entire thing onto the car?

I was considering the Flowmaster Slimline but they seem to be discontinued.

And what about adding those baffles that slide into the tail pipe?
 
#116 ·
They were discontinued. Might give them a call and see if they can do another run. There is no fiberglass in these mufflers. Each end has a cone shape pointing inwards with lots of holes and a double skin to help keep the outer shell cooler but it does increase the overall diameter of the pipe.

The FFR pipes do have fiberglass that will eventually burn or blow out.

George
 
#118 ·
I purchased a set of 24" mufflers from Classic Chambered Exhaust for my car. They have a website and are easy to deal with. They build quality products and will assist you along the way. 248-889-4364. Mike
 
#120 ·
Looks interesting! Haven't looked into the details too much, but will your heat shields fit?
 
#119 ·
Double post...sorry
 
#121 ·
Come on. Yes they will fit. Lol
 
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