My 96 3800 came with a Flowmaster Cat back system on it. I am not sure how old it was but I did mention that the muffler was showing its age when I install the motor. After 2 years of my use she rusted out. Since I am working on my 93 project I did not want to replace the entire cat back but I wanted to try a magnaflow muffler.

First off, If you have a flow master cat back and you want in splice in a magnaflow muffler you better have a set of torchs and a mig welder. Nothing, I mean Nothing lines up. But it does give us a nice comparison of the mufflers on the same car with the same pipes. Just for reference my car has OBX stainless headers and gutted cat. I feel no differents in the car. I am sure that the stock Cat S pipe is the biggest restriction in the system.

Flowmaster. I liked my flowmaster sound at low RPMs. I got a lot of compliments on the sound and everyone I told it was a v6 was surpised. I am talking about car show guys too. The car had very deep tone up to 2800 RPMs. The down side was after the car hit 2800 RPMs it becomes raspy and with a stick when you let off the gas, wow, it sound like a 4 banger. I got to the point if someone was in the car I just pushed the clutch and used the brake to slow down. The drowning at highway speed was pretty bad but a lot worse after the cat was gutted.

Magnaflow. I am sorry to say it does not have the full deep idle. I do not think any car guys are going to mistake it for a V8 but the car sounds much better 2800-3500 RPMs (I have not taken it over that yet) and the horrible noise the car made on deceleration is at about 1/10th of what it was.

I will miss my flowmaster but I think all in all the magnaflow is a better muffler. I am looking forward to Mondays drive to work and being able to hear the music a lot clearer

 

Gorn I have a question for you. I have a flowmaster muffler on my 3800 as well. Many times guys have come up to me and asked if it was a v8 and it makes me laugh but you couldnt have said it any better on the way it sounds when you get to 3000 rpms or so. Here is my question.....I received a set of pacesetter headers from my father last christmas and I am finally ready to put them on. I am trying to figure out if I should stick with the flomaster or change out to magnaflow? I was thinking of going with magnaflow but what do you think would sound the best for this setup?

 

It is going to depend on how important the V8 sounding idle is to you, now that I have put some miles on it I like the Magnaflow muffler better and would not go back to the Flow Master even if I could for free. It was nice to surprise my car friends but I am done with that anyway since they all know it’s a V6 . Like a said I am focusing on my 93 project but I am kind of regretting not getting the whole Magnaflow system. I am surprised how solid the aluminized Flow Master pipes are after 10 or so years. I found no weak spots and the pipe welded up fine after I wired brushed the Aluminum off.
I did have to install the Magnaflow muffler upside down and I hacked up my Flow Master tail pipes to make them work.

 

Yea I am planning on welding on a magnaflow cat on as well so i just figured that i would make the cat back magnaflow too. I do like that you said it sounds good at 3000 rpms though. That is one thing that makes me cringe with my flowmaster. Do you think that with the header upgrade that the rasp of the flowmaster will go away at the higher end torque?

 

Mine has about the same design header as you are about add but I never drove my car without headers so I can not say about the differents. I know when i did the Cat delete the drowning got bad. I do not miss that on the open road.

 

Hm interesting. Alright appreciate the help. Btw excellent threads of the rebuilds you have done. They look most excellent.