Hi all,

Here's the deal. I did the 4.6 to 5.4 swap a while back for towing. I also added long tubes with cats, the best ignition components I could get, and custom tuning. I didn't touch the stock 2.5" exhaust. Here is the issue:

- Whenever I get on the throttle hard, it sounds like someone is hammering on my muffler with a hammer. Sounds like crap. My guess is that now I'm flowing more air, the pressure wave is smacking the flat surface on the back wall of the inlet side of the muffler causing the racket.

A reputable source told me to try a magnaflow no shorter than 24" to avoid having any drone in the cab. I thought while I was at it I would add a 2.5" magnaflow mandrel bent tailpipe to help a little with flow. The problem is which magnaflow? I know the longest flow-thru oval is 24" and rounds can go up to about 27", but what configuration do I want? Offset, offset; center, offset; center, center; or?

Thanks

 

To me it sounds like the original muffler is just shot and ready for replacement. No big deal at all. It has been awhile since I seen a '97/'03 exhaust, so offset locations you would have to look and measure yourself.

As far as exhaust, you can keep it 2.5" or upgrade it to 3" for only a little more high end horsepower. Won't help low end at all, if anything it will take from it. But the longtubes will definitely help make up for low end energy with the free flow.

Do you not want to hear a lot of exhaust noise? You will need the biggest oval body muffler you can get. You want noise but not a lot of interior rumble? Short body oval muffler. If you can handle inside noise, and neighborhood rumble, a round body in smallest form ( 4" round 14" long ). Pretty much, oval bodies keep sound low at low rpm and inside, round bodies are raw loud all around.

These universal mufflers they provide are all designed in sizes for preferenced drivers. If you want some exterior sound that doesn't interrupt neighbors or inside the truck, I would suggest you an oval body 18" case muffler. The round body mufflers I believe do not have offset options, just center in/out.

 

Since I tow heavy loads at highway speeds, drone in the cab at 3500 rpm is NOT an option.
I considered 3", but the effort for a self install for all ss is not worth the hassle. I figured the 2.5" with a mandrel bent tailpipe would net me the best gains for my purposes for collectively about $200.
Magnaflow suggested the oval too, but I don't know about configuration. The total offset on the stocker is about 5" centerline to centerline. Should I go center/offset on an oval?

Would a 27" long round still cause droaning?

Thanks

 

I would stay with 2.5" then.

The 27" case should be more than enough for quiet. Might even be more quiet than stock. With your longtubes, I would choose that, or the next size smaller.

As for offset, again I haven't a clue. Measurements will net you a rendered result on what to pick, all I know is a center in/out won't work.

 

So if a center/center won't line up, it rules out a round muffler right? ... or can I manipulate the tailpipe or buy some type of adapter to make it work?
I have yet to see any manufacturer list offset dimensions on mufflers. Is there a standard?

 

If you don't want a lot of inside noise I would rule out a round muffler overall.

If you have enough length of tubing between the new muffler to the older pipe, you could have a pre-bent pipe inserted to make the connection. This almost never works unless it is done by a shop and a bender though.

Here is Magnaflow's muffler offering and offsets.
http://www.magnaflow.com/02product/universalmuffler.asp