Magnaflow Cat Back- UPDATE, system installed

[BurbMan]

It's muffler time again....Back in 2012 the OEM muffler rotted out and I replaced it with a Flo-Pro (see this thread) because I was concerned about interior noise, specifically droning while towing.

So, 4 years later and the aluminized Flo-Pro is now junk...I couldn't replace it if I wanted too, Flo-Pro still shows it on their website, but looks like they stopped making it since none of their dealers list it on their sites.

My only options are either a MagnaFlow or Gibson Stainless cat back system, so I decided to roll the dice and I ordered the Magnaflow #15716 system.

The 8.1L wasn't that common, and even less so in the Suburban/Avalanche configuration, which has a different exhaust set up than the HD pickups. GM only sells the entire cat-back system as an assembly for the low low price of $1900. I got a 20% off coupon for Planet Magnaflow and got the system for a little over $500 shipped, which is what the local muffler guy wanted to fab a fitz-all steel muffler onto the truck.

My local mechanic said he would do the install for $150 or so. It needs to be done on a lift, the muffler is the size of a garbage can and there's just not enough room to work with just jackstands....I tried last time LOL.

So the ol' burb keeps rolling on....

[larry_barnhart]

I had this loud problem on our 2001 8.1 and the dodge before that using this muffler. The fix for us was a resonator exhaust pipe tip at the end and that did just enough to keep us sane. Going to the duramax was a blessing for our ears.

chevman

[normal_dave]

I put a Magnaflow muffler that seemed nearly as big as a suitcase on my Ford Club Wagon. It is nice and quiet at idle and overall, but towing in overdrive, it does setup some drone in the cabin at lower highway rpms. Locking out overdrive, it is fine.

You could do the old school trick, just have your muffler shop install a resonator muffler near the axle right before the tailpipe exits the vehicle. Shouldn't cost much, should really help the drone, and I doubt, that far back in the system, it would hurt airflow at all. If you wanted to stay fancy, just pick a short magnaflow cylindrical muffler to go inline. If they still make them the "baloney" shaped steel pack, cheap muffler would work, but if you have road salt to worry about, then get the magnaflow equivalent in stainless.

Edit: my last daily driver was a 4.6L Mercury Grand Marquis LSE (forerunner of the Marauder), factory dual exhaust, with factory h-pipe, factory resonators in the pipe just before the tailpipe turndowns. Swapped factory Mufflers for Magnaflows, could hardly tell I had them installed. Later had to remove the factory resonator mufflers to be able to notice the change.

[BurbMan]

So the issue here is not whether a cat back is worth it. Banks said early on that they were not making a kit for the 8.1 because the factory exhaust was so efficient that no gains could be gotten. (Only exception was the 8.1 on the Workhorse Class A chassis.) This is why in 16 years of owning this truck I have never felt the need to install a cat-back exhaust system.

The issue is that nobody makes a muffler for this truck.

Chevy only sells the muffler and pipes as an "assembly" for the low low price of $2000. Flo-Pro made an exact fit muffler for this truck, but it's been discontinued since they sell 100% diesel exhaust now.

UPDATE:

The new system has a single side-exit pipe, just like the stock, except it's upsized from 2-1/2" to 3". Had the system installed by a local shop and I will say it sounds bad-azz!!!! If you want to turn some heads and rattle some windows, nothing beats an 8.1 with a loud muffler! The truck now has a seriously cool factor to it.

Now for the not-so-good news....if you thought it was loud when you got into the go-pedal, hitch up a 9k travel trailer and hit it....now we are talking LOUD!

So far DW doesn't seem to mind, but this is way louder than I would like it to be when cruising the highway with the TT in tow. It drones really bad around 1500 rpm, but not an issue for me since the engine is usually at 2300 or so cruising and 3200 if in 3rd gear pulling a hill.

Good news is that it doesnt drone badly when towing but man this thing is LOUD. It's a quality kit, so I would definitely recommend as far as that goes. Towed about 2 hrs home today and I'll admit I was getting used to it. If you are looking for a louder exhaust for your big block, this is the kit for you!

Will try to post a sound clip when I get some time.

[Terryallan]

Burbman. Ask your mechanic IF he really thinks the cat back is worth it. my mechanic, (after I already had one put on by another) that because the pipes coming out of the engine to the cat were no larger. The engine was still pretty restricted, even opening after the cat really didn't do all that much to let air flow thru, and I could have got pretty much the same effect by simply installing a good flow thru muffler.

That I did open the intake did help. remember. If you open the outflow, you got to open the intake to see any gain.

[BurbMan]

Steve, I already replaced all the brake and fuel lines in 2013 with pre-bent stainless lines from Classic Tube.

Terry, stock exhaust exits to the side behind the RR tire. Don't have a cat-back today and can no longer buy just the muffler, so am adding a cat back system.

[Terryallan]

To ease the droning in the cab. Run the pipes out the side and not the back Out the back the sound bounces off the trailer. Out the side if don't

Also if you already have a cat back. Why can't you just replace the muffler and not the whole thing. That's what I did

[STEVEO496]

Let us know how it sounds. I have a feeling mine's going to need a muffler before too long. My truck doesn't get driven enough, therefore the water doesn't get burned out of the exhaust system sufficiently. Do yourself a favor and inspect the steel brakes lines while the truck is on the lift. I had one bust on me last weekend. I had just purchased a new to me travel trailer 3 hours from home. I hooked to it and pulled out onto the road and the brake pedal went to the floor. Lucky for me and everyone else on the road it happened where it did. My truck is low mileage and doesn't have a spot of rust on it anywhere except the brake lines :M