Stainless exhaust build

[GTP091]

Im currently building a custom 304 stainless exhaust for my GTP.  Has mafnaflow hi flow cat downpipe. And 2 magnaflow mufflers and tips.  I’m wondering on putting a resonator on or not. Does anyone have any experience with doing a custom exhaust on a 3.4 without adding the resonator? I’m not a big fan of drone but would rather not put on a resonator if it won’t make much difference.

[55trucker]

The resonator won't restrict flow at all, it WILL tone down some of the drone the magnaflow's produce, and they will. Some many years ago I purchased a pair of 11225 mufflers when I was redoing the exhaust, shortly after they were under the car they immediately came out. Far too loud for my purposes, I like to be able to hear the sound system at something a little above a whisper. 

I redid the exhaust in 2 1/2" back to the split, I included a new resonator located alongside the fuel tank. What I used was a DynoMax 2 1/2" racing bullet muffler, it's basically a straight thru resonator (not really a muffler), if you don't want drone then you more than likely will not want the magnaflow's. In the end I went with a pair of Maremont C series universal aluminized installer items, (Maremont no longer exists). That was 17 years ago, I just recently replaced the left side muffler as it finally rotted out. Seeing as the car only sees use in the summer they survived well. I'm sure that you can find a stainless bullet resonator in today's market.

Edited January 18, 2021 by 55trucker

[GTP091]

The tips are resonated so I’m hoping that’ll be enough.  As long as I don’t end up with anything close to a 4 banger wound up sewing machine sound I’ll be on the right track.  I’m using vbands through out so it’ll be very easy to remove the section by the tank if I don’t need to put a resonator in. 

[55trucker]

Well it won't sound like a 4 banger, but the drone I experienced was a deep tone at idle that progressively got louder up to 2000 rpm (highway cruising rpm) then tapered off, at wot it was even louder. With what I have under the car right now it has a deep burble that is not intrusive, but redoing the exhaust gets rid of that obnoxious raspy tone that the original system was infamous for.  

[GTP091]

I blew right by the tank on the way to the back today so no resonator. I listened to a bunch of different exhaust systems on inter webs today and figure I’ll go without the resonator. If it ends up with to much drone it’ll be easy to add later on. Will post up some pics when done.

[55trucker]

Because 17 years ago stainless was still hard to come by (here) I did the entire job in aluminized, 4 years ago I redid the intermediate section in 304, I had to cut everything to precision fit & then butt welded it all together. it will outlast the car.

You will enjoy the same.....

 

Edited January 19, 2021 by 55trucker

[GTP091]

Had to build a y pipe so that set me back a day or two.  Original magnaflow Y’ was to long and I coudnt make the turns into the mufflers with it. Also realized it was a merge pipe and would have been bad for flow. Still need to finish the tack and size the last two bends. Good progress though. Pipe in the right is almost at the height I want. Another 1/2” up and should be good. 

Edited January 28, 2021 by GTP091

[55trucker]

I take it that you still have the hanger assembly for the rear section of the exhaust that is fastened to the suspension member?

[GTP091]

I’m going to rebuild it out of stainless but will be in the same spot.  Same as the rest of them.  I did go to the JY and found a few good OEM rubber hangers to replace one  I lost in the rear during the tear down. 

Edited January 29, 2021 by GTP091

[GTP091]

Well shit never goes to plan wrenchin on cars.  I found the pipe ordered didn’t have quite enough bends to get the mufflers tucked up like I wanted them. Ordered two more 45s to lift the inward side of the mufflers up another two inches. They sent two 2.5s instead of the 2.25 I needed. A few more days and they should be here.  I guess that I get to keep the incorrect tubes though, my f150 is getting worried now.

Edited February 12, 2021 by GTP091

[55trucker]

^Well I was going to suggest to you that before you begin to assemble the rear section to hang in place everything up to the Y split & finish that portion off so it is placed at the height it needs to be & then begin cutting & assembling the back end, but you had already tacked the back end together in the pics you provided. In those pics the system seemed to be hanging on the low side. Is everything still just tacked together?

[GTP091]

Nothing is tacked together yet in the back.  The mufflers were just mocked up in the pictures so how I realized I needed more pipe to raise the mufflers a bit more. The y pipe is higher up than stock by just under 2 inches. 

[55trucker]

I'm just guessing that because the tips are straight you have to keep the muffler down lower to align the outlet of each muffler to the inlet of each tip so the tips both clear the rear bumper cover cutout. I don't have that issue at all, when I did mine the mufflers are tucked up close to the floorpan & I made use of a pair of * S bends* to drop the pipe height and align the tips which hang lower than the mufflers do.

[jman093]

My old 96 LQ1 GTP had that essentially same exhaust setup except for the stainless tubing. Magnaflow high flow cat, straight-thru style resonator, and dual magnaflow mufflers in the back. It was incredibly loud. It sounded fantastic don't get me wrong, but sometimes the constant noise on the highway would get to ya, and the car was my DD so a lot of neighbors hated me.

[GTP091]

The correct pipes came today so I can get back at it now.  They sent a free toque!

[55trucker]

Now  isn't THAT a coincidence, Lyell's is where I go to to get all of my tubing!

The only difference is I can drive to Burlington to get it.

[GTP091]

Got the left test fit on nicely.  It’s all tucked up where I want it.

[GTP091]

The other night I broke the crank on my vise and the armature on my chop saw burned up and chewed the brushes to bits so got no way to properly finish this up. Not going to hack it, so need some replacement tools now. Good thing it’s a project car and I’m not driving it.  Almost have the mock-up finished. Really wanting to get the y-pipe hanger in place before I make the final weld on the passenger side muffler so shit doesn’t move around when I take the supports away. 

Edited February 28, 2021 by GTP091

[55trucker]

12 hours ago, GTP091 said:

The other night I broke the crank on my vise and the armature on my chop saw burned up and chewed the brushes to bits so got no way to properly finish this up.  so need some replacement tools now.

LOL, you have discovered how much more brutal stainless is where trying to cut it is concerned, it is considerably harder than mild steel. I went thru a couple of 14" cut off discs with my chop-saw as well. Didn't kill the motor tho, backed off the pressure to save the motor. what brand of chop-saw do you have?

[GTP091]

I’ve worked with stainless lots before so isn’t my first rodeo here. I was actually cutting some regular old steel for non car purposes when she burnt up.  The saw is a very old craftsman and my vice has been abused over the years.  Just a pain in the ass when they both bust up the same day. 

[55trucker]

Know where you're coming form, mine's just a Princess Auto special, motor isn't heavy duty so one has to pay attention so as to not overload it, other than that it works well.

[55trucker]

Did you get your chop saw replaced?.......how's the project coming along?

[GTP091]

Ran out of 308 and just got another roll delivered today.  Also just picked up a new vice to finish the y-hanger.  Back at it tonight. Hope to be done soon.  Street sweepers are out and I’d like to get it insured once they’re done.

Edited March 16, 2021 by GTP091

[Regal]

Nice! I put a Magnaflow dual outlet muffler and cat on a 4.9 Cadillac I had. No resonator needed for sure on that motor! I would have suggested not to bother on this one either. Am looking forward to doing something similar on the Buick with Magnaflow again but routing for the dual exhaust look I'd want is going to be something to figure out.

[GTP091]

13 hours ago, Regal said:

Nice! I put a Magnaflow dual outlet muffler and cat on a 4.9 Cadillac I had. No resonator needed for sure on that motor! I would have suggested not to bother on this one either. Am looking forward to doing something similar on the Buick with Magnaflow again but routing for the dual exhaust look I'd want is going to be something to figure out.

I’ve fired it up recently after getting the last muffler and tip tacked up, couldn’t resist..  it sounds pretty good so far idling but won’t really know on the need of a resonator until I get it out on the road and see how it sounds at 4200 rpm when it opens up under load. Soon enough!