If you're not above a little cutting and welding, you can make them work.
My old Flowmasters, which were on the car when I bought it, were completely hollowed out by rust. One of started rattling a couple of months ago and when I took it off to investigate, there was almost nothing left inside it and I found a piece of broken off baffle halfway blocking off the tail pipe where it got lodged just before it turns to go over the axle. Removing the obstruction took care of the "water-hammering in your house plumbing" sound that had developed and the rattles mostly went away as the offending pieces finished disintegrating. Right before Christmas though, the sound levels got intolerable and there was a massive droning and low frequency thrumming in the cabin. When I took the other muffler off while I was replacing them I found that it had split up the side and there was a hole the size of a salad plate in the top of it
I went with S197 mufflers because they're high quality OEM stainless steel mufflers that should last a good long time, they should be good for at least 300HP which is more than I'll need for a while, and best of all, they are cheap! $40 for a pair of them and they're practically new. They are not a direct bolt in or weld in piece though - some, um, assembly required.
I'm very pleased with how the project turned out, mostly because I was able to actually finish it successfully having never done any serious exhaust work before.
How do they sound?
The S197 mufflers are quieter than I was expecting - I knew they were going to be quieter than rotted out Flowmasters but even for being OEM mufflers I was surprised by how quiet they are with the offroad H-pipe. They're about the same volume as the Flows with the factory 6-cat H-pipe was (I think, it's been a long time since that setup) but the Flows (with cats) were a little deeper sounding and the S197s (without cats) are a little smoother and refined sounding. I was hoping for just a little more volume but I'll get use to it, plus they were so loud for the last few weeks that my scale of what's loud and what is quiet is still completely thrown off.
They sound good at WOT and sound strong at high RPMs. Part throttle is much more pleasant now, especially between 2000-3000 RPM. The engine feels smoother below 2000 RPM - the electric motor smoothness of the 4.6L is back. No drone or obnoxious 2100 RPM resonance anymore. Doesn't feel like I lost any topend power but at least in normal driving, the car feels faster because I can use more throttle and more RPMs without attracting unwanted attention.
All in all, it sounds similar to my buddy's stock 2007 GT, which shouldn't be too surprising I suppose. Definitely an American V8 but it's civilized.
Sort of technical info:
For reference for anyone else who (is not in their right mind and) wants to try this at home...
S197 mufflers are slightly larger in every dimension than the Flowmasters were (I'm assuming they were same as stock SN95 sized mufflers) and the center distance on the inlet/outlet was a bit wider too so you can't just pop your old ones out and pop these in. They're also pretty heavy (a lot heavier than gutted mufflers
), if that matter, but I didn't weigh them.
You'll need to cut the curved inlet pipe and the outlet tips off. I cut the pipe clamp section of the inlet off and welded that to the outlet and used it to attach to the remaining section of tailpipe in the car (I cut them right behind the old mufflers). I trimmed a section of 2.5" pipe and welded it to the inlet and then the old flowtube off the car, after cutting off the old muffler, that attaches to the H-pipe. I had to cut the front hangers brackets off the S197 mufflers and then I took whichever combination of pieces of old and new hanger brackets worked best to locate the rubber hangers properly and welded them up.
I was able to get the S197 mufflers a little tighter to the car than whoever put the Flows in did so they don't scrape on the 137 speed bumps in my neighborhood anymore (yay!). I still need to adjust the hangers a little bit to get them more even but nothing a BFH won't fix. Due to the extra width of the S197 mufflers, I'm not sure I could drop the drive shaft without loosening the mufflers first but they don't hit it at full suspension travel either.
So, for $40 for the mufflers, $5 for a 5 foot section of 2.5" SS exhaust pipe off a Navigator at the pick-n-pull and $20 for a couple lbs of 309L SS welding rods plus a good day of cutting, grinding and welding in the garage (a skilled welder with better equipment could do it a lot faster), and I'm pretty happy, even if it's a little quieter than I was expecting.
My old Flowmasters, which were on the car when I bought it, were completely hollowed out by rust. One of started rattling a couple of months ago and when I took it off to investigate, there was almost nothing left inside it and I found a piece of broken off baffle halfway blocking off the tail pipe where it got lodged just before it turns to go over the axle. Removing the obstruction took care of the "water-hammering in your house plumbing" sound that had developed and the rattles mostly went away as the offending pieces finished disintegrating. Right before Christmas though, the sound levels got intolerable and there was a massive droning and low frequency thrumming in the cabin. When I took the other muffler off while I was replacing them I found that it had split up the side and there was a hole the size of a salad plate in the top of it
I went with S197 mufflers because they're high quality OEM stainless steel mufflers that should last a good long time, they should be good for at least 300HP which is more than I'll need for a while, and best of all, they are cheap! $40 for a pair of them and they're practically new. They are not a direct bolt in or weld in piece though - some, um, assembly required.
I'm very pleased with how the project turned out, mostly because I was able to actually finish it successfully having never done any serious exhaust work before.
How do they sound?
The S197 mufflers are quieter than I was expecting - I knew they were going to be quieter than rotted out Flowmasters but even for being OEM mufflers I was surprised by how quiet they are with the offroad H-pipe. They're about the same volume as the Flows with the factory 6-cat H-pipe was (I think, it's been a long time since that setup) but the Flows (with cats) were a little deeper sounding and the S197s (without cats) are a little smoother and refined sounding. I was hoping for just a little more volume but I'll get use to it, plus they were so loud for the last few weeks that my scale of what's loud and what is quiet is still completely thrown off.
They sound good at WOT and sound strong at high RPMs. Part throttle is much more pleasant now, especially between 2000-3000 RPM. The engine feels smoother below 2000 RPM - the electric motor smoothness of the 4.6L is back. No drone or obnoxious 2100 RPM resonance anymore. Doesn't feel like I lost any topend power but at least in normal driving, the car feels faster because I can use more throttle and more RPMs without attracting unwanted attention.
All in all, it sounds similar to my buddy's stock 2007 GT, which shouldn't be too surprising I suppose. Definitely an American V8 but it's civilized.
Sort of technical info:
For reference for anyone else who (is not in their right mind and) wants to try this at home...
S197 mufflers are slightly larger in every dimension than the Flowmasters were (I'm assuming they were same as stock SN95 sized mufflers) and the center distance on the inlet/outlet was a bit wider too so you can't just pop your old ones out and pop these in. They're also pretty heavy (a lot heavier than gutted mufflers
), if that matter, but I didn't weigh them.You'll need to cut the curved inlet pipe and the outlet tips off. I cut the pipe clamp section of the inlet off and welded that to the outlet and used it to attach to the remaining section of tailpipe in the car (I cut them right behind the old mufflers). I trimmed a section of 2.5" pipe and welded it to the inlet and then the old flowtube off the car, after cutting off the old muffler, that attaches to the H-pipe. I had to cut the front hangers brackets off the S197 mufflers and then I took whichever combination of pieces of old and new hanger brackets worked best to locate the rubber hangers properly and welded them up.
I was able to get the S197 mufflers a little tighter to the car than whoever put the Flows in did so they don't scrape on the 137 speed bumps in my neighborhood anymore (yay!). I still need to adjust the hangers a little bit to get them more even but nothing a BFH won't fix. Due to the extra width of the S197 mufflers, I'm not sure I could drop the drive shaft without loosening the mufflers first but they don't hit it at full suspension travel either.
So, for $40 for the mufflers, $5 for a 5 foot section of 2.5" SS exhaust pipe off a Navigator at the pick-n-pull and $20 for a couple lbs of 309L SS welding rods plus a good day of cutting, grinding and welding in the garage (a skilled welder with better equipment could do it a lot faster), and I'm pretty happy, even if it's a little quieter than I was expecting.
