DIY stock muffler mod, 1 out to 2 out, SC

Tim Hancock · 06:47 AM

Recently converted my '79 SC stock 1 in/1 out to 2 out. Timed 2nd gear 30-60, 40-60, 30-50mph tests showed basically no difference in performance, but it definitely sounds more aggressive. The flange mounted tip allows me to bolt in a restrictor plate or block it off if I want. (It sounds good like it is though)

I cut a 2 1/4" dia hole in right muffler chamber then pulled packing out thru hole thus exposing 180 deg perforated tube.

Next I inserted and tig welded short 2 1/4" dia nipple to the new hole. To this I welded a newly fabbed flange.

Next I obtained a pc of scrap 2 1/4" exhaust tubing from a local Midas that had a bend that looked about right. I cut this to fit and welded the other flange I made to it.

Next I carefully cut asection of my rear valence off.

I finished the job off w/ some cheap modified stainless tips from a Advance Auto Parts store ($8.99 each). The whole project cost me $17.98!

mb911 · mb911's Garage

tim stop these post it can't be good for my sales

Tim Hancock · 06-27-2005, 07:31 AM

No worries Ben, I know yours is way lighter and probably sounds better.
If I ever decide to BUY a muffler, I can garantee it will be one of your 321 stainless bad boys! (because I can hardly even buy the material for what you make the high quality finished product for. I just know you robbed a trainful of aircraft grade 321 at some point!)

Having scratch built some airplanes, being a mechanical engineer and having a wife who cannot understand how I have spent almost as much as I paid for this car one year ago, means that these kind of projects are likely to happen from time to time!

Paulporsche · 06-27-2005, 07:36 AM

Nice work and thanks for the test results.

tdatk · 01-07-2006, 12:22 PM

Tim,
Is the sound balanced from side to side? I've read that happens if you open up that end up more than 1/2" or so. Looks great. Did you modify the rear valance as well? pics?

Wavey · 01-07-2006, 01:23 PM

Wow - very nice fabrication, Tim!

Tim Hancock · 03:46 PM

tdakt, I guess I missed the resurrection of this thread awhile back otherwise I would of responded.

Other than the photo above showing my tip exiting the rear valence, I do not have any other pics at the moment. I carefully cut the valence after measuring the opposite side for reference. The forward part of the opening is actually (on an SC at least) the lower rear rocker (or whatever it is called) which is a vertical edge compared to the stock left side which angles slightly. I chose to leave this part alone as you cannot see both sides of the car at the same time. I cut off 6 1/2" (measuring along the top flange with a flexible ruler) off of the right side off the rear valence.

I used aviation snips to cut carefully make a clean cut. After wards I slightly rolled this edge to duplicate the look of the left stock opening. My rear valence needs repainted eventually due to some previous repaint flaws, but I just used touch up paint along the raw edge. Unless you know about it, it is pretty un-noticable. I saved the cut off pc so if I ever want to go back to a single out system, I can simply tig weld it back on.

As far as the sound difference from left to right, well it may be different but I did not notice any issues while standing behind it with sme one else revving it up. It is kind of loud and after driving it daily 80 mile round trip last summer and fall, I am ok with it. If I were to take it on a long trip with my wife, I might consider bolting a restrictor or block off plate in between my flanges. With my setup, and the anti-sieze on the stainless bolts, it would take me about five minutes if that!

With a 1 in system, it does not really matter if one sides flows slightly different than the other so side to side balance is not critical and unless someone is checking it with a sound meter, it does not matter to me.

I really thought I would need a restrictor plate, but I am guessing these mufflers changed inside from different model years and mine just did not really need it.

tdatk · 03:53 PM

Thanks for the quick resonse Tim ...J/k

I have a spare stock muffler I want to play with and your idea seems simple and clean. Nice work.
I just moved from Perrysburg, Oh in 2003. Sorry I missed ya. "You'll have that"

Tim Hancock · 01-26-2006, 04:06 PM

I am in P'burg on occasion (I work in South Toledo). I have d had my BMW at Bavarian Auto in P burg for diagnostics a couple of times. Small world (kinda!). FWIW, my setup sounds kind of V8-ish at idle, but I think it sounds pretty good once the revs come up. The price is definitely right and I have fun messing around with these type projects.

Good luck with yours!

tdatk · 01-26-2006, 04:19 PM

Ya, I had my 944 to Bavarian auto for cam and injector diag. The only show in town as they say other than the Porsche Dealership in Toledo, and they got zero business from me, I didn't meet their criteria for respect...

Yellowbird RS · 01-26-2006, 04:30 PM

Can you upload a sound clip?

Tim Hancock · 01-26-2006, 04:49 PM

Sorry, I do not have one. I did try recording it on my digital camera in video mode, but it was not very good. I do not think it is possible to post a video/sound clip on these forums is it?

Jadams1 · Jadams1's Garage

Nice Work!

RickM · RickM's Garage

Quote:

Originally posted by Tim Hancock
Sorry, I do not have one. I did try recording it on my digital camera in video mode, but it was not very good. I do not think it is possible to post a video/sound clip on these forums is it?

If you have a Windows laptop with a built-in microphone you can easily record a clip. Go to "Accessories" -> "Entertainment" -> "Sound Recorder" . After you record I'm sure someone here can host for you.

FWIW, I had done this mod years a go and like it alot. Balance of sound from side to side has never been an issue for me.

Yellowbird RS · 01-26-2006, 08:26 PM

Free video hosting

Tim Hancock · 01-27-2006, 03:52 AM

I will see if I can get a clip hosted somewhere if I have time this weekend.

Wil Ferch · 01-27-2006, 05:48 AM

Tim:

I have what you did but went that extra step in making the right-side valence cut "more closely" match the left side.

The cut on the right side of the valence kept a portion of the valence near the top-side and the forward cut ( toward the *front* of the car) was angled about 45 degrees...to mimic the sloped shaped you see as part of the left-rear rocker panel. I also formed a "lip" as you did in the cutout....I agree it makes for a "finishing" touch.

Wil

NoLift911 · 01-27-2006, 07:45 AM

That looks really nice and great welding...I have a similiar setup on my 84 although I did not do it. I got the muffler kit from RUF.

It looks like they took the stock muffler cut it open and made some mods internally in addition to adding the second outlet.

The flow air wise, and sound is very similiar on both ends. The kit also came with a mirror copy of the driver side valence for the passenger side and looks oem. It was a great mod but $$.

I didn't have a welder or a decent die grinder at the time but I do now and have a spare Carrera muffler so I may undertake this if anyone is interested.

-Jeff

toolman · toolman's Garage

Hey Tim, PM me a way to get in touch with you, I might have something you need.

Tim Hancock · 01-28-2006, 06:58 AM

PM'ed you Toolman. Give me a call today if you want. I have my cell w/ me if my home ph is tied up on the internet.