Stainless Specialties muffler mods...
 

Ever since I was one of the first to install a custom muffler onto an SPF (see link below), I have been constantly asked every question under the sun regarding these.

http://www.clubcobra.com/forums/show...ss+specialties

More recently (the past year) several that did this have also noted a "fluttering" sound that is very distinguishable on deceleration. The cause appears to be the abrupt right angle of the weld that holds the perforated center section to the outer casing (stock SPFs have a cone like piece of metal that helps eliminate the same issue on their much smaller 2" ID factory mufflers). Given all the PMs and such, I can't recall who proposed doing the following mod:

http://www.clubcobra.com/photopost/d.../scan00021.jpg

CC member "carmine" has been considering doing something, so I whipped up the above drawing using Excel and converted it to a .jpg. As least this is how I perceived the mod based on a series of e-mails (long since tossed) that I shared with someone here! I'd like to hear if anyone has performed this mod and what the results were? It looks logical but would obviously require cutting them open and a complete ceramic re-coat (both of which I can't afford at the moment). But if this is the ticket, then I'm game for figuring out a way (Brian, are you listening)?

The whole Stainless Specialties muffler mod has been beaten to death here before (just do a search to confirm). But no one that I can recall has documented any mods to them to eliminate the very annoying fluttering sound when easing off the pedal and coming toward a stop.

Thanks everyone,

-Dean

Dean,

You may be combining several side pipe issues that have been discussed. I welded on a transition on my 3" bore side pipes to smoothly funnel exhaust into the 3" muffler from a 3.5" collector similar to the way you indicated. I just didn't want any abrupt walls to impede the flow when it could flow smoothly. I don't have stainless specialties mufflers though.

Then again, I may be wrong and never saw a thread or two about this.

R

Timely Post
 

Red,
Great timing on this post as I am in the process of removing my S/S mufflers (cutting them out) & sending them back to them for replacement.
Mine were great for the first 5-6000 miles then they started to get continually louder the socond season untill they are now unbearably loud after about 10,000mi. I inspected them the other day with my borescope & discovered there is virtually no packing left in them.:(
Now I have to say John @ S/S has been great about the problem & has offered to replace the mufflers with a "improved" version including all shipping cost. Can't expect much more than that.:)
While speaking with him I discussed this exact modification with him, he said they have never found it was ever necessary according to their their test results.
I also have that "fluttering sound" & also get a occasional tweeting or chirping sound from mine. (not a very cool sound :o) So I would also be very interested in learning if this mod does help.

Thanks again Craig

Anything that acts like your tongue when you whistle will do the same in exhaust.. The reason the system got louder was 2 things. Residue from the exhaust sticking to the packing, and making it a straight through pipe. Or the packing itself burning out.

The packing material is a "ceramic blanket". I too looked at it and figured that it wouldn't be long before soot coated it good and the pipe eventually would become louder (which it has after about 3,000-4,000 miles of use).

Craig, keep me posted on your progress. I sent a $#!tload of business to John (he will remember me if you mention my name) and I wouldn't mind an improved version as well.

-Dean

Ron, it's been discussed but never documented. I think it was you that I traded PMs with. Based on the drawing above, is that approximately how you welded up your transition cone? Or was the section that you used too long and your welds were closer to where the collector joins the straight pipe?

-Dean

I welded one of these cones on each side in the collector just ahead of the stainless specialties mufflers. I've never had any noises - other than really loud sidepipes. :LOL:

SPF1061
Interesting cones. Where did you aquire them, or did you fab them up?

Craig

Wow, another Yorba Linda Guy!!!!!
Please PM me with your telephone number
I am in East Lake

cdnus

I'm also very happy with this cones. You can buy it from Dynatech:

http://www.afabcorp.com/AFCO_Dynatec...rtex_conesonly

http://www.afabcorp.com/AFCO_Dynatec..._Code=Dynatech

Greetings from Switzerland

Walter

Craig,
They are made by Dynatech. I bought mine on line from Summit.
-Steve

Insteresting... do the cones really work??

I sure could use some horse power fiendly sound deadening out of my 4 " side pipes.

Dave

Steve,
Do you have a before & after comparison or did you install the cones from the get go?
Their site claims a 1-3 DB reduction---not much if the noise level is very high.
I should mention that I went with the 2 1/2" core not the 3" because I wanted a somewhat bearable sound level & to start with thats exactly what I had.
The reason I mention this is the 2 1/2" has a even more pronounced step @ the core, perhaps causing even more internal turbulance creating the strange sounds.

Craig

Dean,

My muffler pipes were constructed different as I had the Classic Chambered mufflers. But your drawing is very similar in pricipal to what I did. If I had your mufflers, I would do it just the way you have your drawing.

You should build a welding fixture if you plan on doing this often.

R

Thanks, Ron. I do not have my own welding equipment, nor the skills. But I can turn a wrench with the best of them. :)

RedBachetta,
You have a P.M.

Craig

Craig, thanks for the info.