Aftermarket muffler close in sound/db as OEM

darth_linux

New Member
Joined
Oct 9, 2022
Messages
47
Reaction score
38
Location
Spokane, wa
I'm curious - were our C-Bodies "quiet" when new, as compared to say the more performance oriented cars of the time? I'm thinking specifically about Slab Bodies, but any answer is appreciated. I can't imagine a New Yorker sounding like a GTO or Corvette of the day.

Is there an aftermarket muffler that is as quiet or nearly as quiet as original, but perhaps flows a tiny bit more? I read a few people talking about the OEM "Hemi" mufflers, but I don't know where to find those, or how quiet or loud they actually are.

thanks for your thoughts!
 

carguy300

Active Member
Joined
Jul 29, 2018
Messages
257
Reaction score
127
Location
East Texas
My brother put hemi mufflers on his 318 fury, duals. Was very agressive, I had duals with stock mufflers on 68 300, 440. Had a nice mild idle and fairly beasty when rev up, but quiet going down the road. You can always add a resonator on the tail pipe. A lot new yorkers and imperials back in the day ran them. The 68 300 I have now is single exhaust with a resonator but I have not got it running yet to see what sounds like. In time I will probably run stock duals again.
 

Trace 300 Hurst

Professional Tinkerer
FCBO Gold Member
Joined
May 27, 2018
Messages
2,054
Reaction score
2,494
Location
Ponte Vedra Beach, FL
Big-engined C bods had a quiet burble using big muffler, whereas the muscle Mopars had smaller mufflers with resonators.

When I got my car it had awful, drone-y FlowMasters, installed in 1999 when they were pretty much the only game in town. I went with MagnaFlows, and my car now sounds very correct. Quiet burble, nearly silent going down the highway, but speaks with some authority when I go to WOT.
 

Trace 300 Hurst

Professional Tinkerer
FCBO Gold Member
Joined
May 27, 2018
Messages
2,054
Reaction score
2,494
Location
Ponte Vedra Beach, FL
I should add that I went with the Magnaflows upon advice of a very old-school, family-owned muffler shop, in business for decades, who sold all varieties of stock and aftermarket mufflers.

I figured the proprietor had a pretty damn good idea of what our cars sounded like, and he nailed it.
 
Last edited:

CBODY67

Old Man with a Hat
Joined
Mar 27, 2011
Messages
8,098
Reaction score
5,169
I have always liked Walker Exhaust OEM replacement mufflers. There is ONE C-body muffler from about 1965 to the 1973 model years. Dual exhausts had the same muffler, just two of them. Talking about 383-440 C-bodies, not sure what the 318 cars had under them. NAPA used to sell Walker Exhaust products under the NAPA name (and the same part number as the Walker items).

There was ONE year where the 440/375 C-bodies had a different muffler, Street Hemi in this case, than the normal muffler. It was the 1969 Polara police car with the 440/375 engine. Other parts of the exhaust system were the same. 1968 and 1970 440/375 cars reverted back to the normal C-body mufflers.

In 1969, the 440/375 police Polara set a top speed record of right at 150mph in the Michigan State Police Car Tests. A record that took a mid-1980s IROC Camaro 5.7L TPI to BARELY best. That particular Polara had a 2.7 rear axle ratio and L84-15 tires on it, for a bit of an overall gearing advantage of the normal 3.2 rear axle ratio, in the top speed area.

The genuine Streeet HEMI mufflers were of the same case sizing, just shorter and with larger inlet and outlet pipes. In that later-1960s time frame, there were only TWO real facctory low-restriction mufflers. The Corvair TURBO mufflers and the Chrysler Street HEMI mufflers. There were MANY imitations, too! The Corvair TURBO dating back to the Corvair Sypder turbo cars of the very early 1960s. So imitaitons of that Corvair muffler was the first use of the term "turbo muffler" in relation to a "performance" muffler, but some were better than others, as some companies wanted a "cheap imitation" to sell lots of them. The OEM Corvair Turbo mufflers were more rounded in the case dimensions, whereas the Chrysler Street HEMI mufflers were flatter, as per normal Chrysler mufflers of that time, and were easier to fit under low-ground clearance vehicles.

What I put under my '67 Newport 383 4bbl car (Chryslers with the 383 4bbl got a factory single exhaust as similar Plymouths and Dodges for dual exhausts) was a "from the y-pipe back" '72 Imperial exhaust system. Seems that THAT application used a normal C-body sized muffler that has very similar flow restriction as the Street HEMI muffler, with 2.5" pipe diameters. It all fit well . . . other than the very rear resonator-eliminator pipe and a simple adapter to the original y-pipe ball joint connection at the very front. My "sewer pipe single exhaust". At the rear, the body contours of the slabs angles upward to the rear bumper whereas the Fuselage C-bodies had a more horizontal line between the rear wheels and the rear bumper. A tweak at the muffler shop, for a slight upward angle fixed that.

In current times, it seems that the ONLY people who like the Flowmasters (the models with the fewest number of internal "flow directors") are the 5.0L Mustang enthusiasts. You can hear them coming, if you know what to listen for!

I believe that if you go into the Walker Exhaust online catalog, you can find the specs for the Chrysler mufflers (as to case size, pipe diameters, and pipe orientations). Walker was an OEM supplier and their stuff was an exact fit for the factory production OEM items. I highly suspect that your car has been "muffler-shop-ized" with a generic muffler of an incorrect length, something they had that "will fit" and is welded to the pipes (rather than using quality exhaust pipe clamps)? By observation, most muffler shops will use a generic muffler of a similar size rather than order in a correct muffler, from my experiences. Nothing really wrong with that, just that what they use is usually not exactly correct. Gets the job done. BTAIM

If not using a Walker Exhaust muffler, then MagnaFlow would be my next choice. Of the correct size and such, of course. And using quality exhaust pipe clamps so that I could change it in my driveway with the car on sturdy jack stands (or on an overhead lift), at least in my younger days. Some muffler shops, around here, were very variable in the quality of the work they did, back then.

Sorry for the length. Just my experiences.
CBODY67
 
Last edited:

saforwardlook

Old Man with a Hat
FCBO Gold Member
Joined
Oct 8, 2011
Messages
7,435
Reaction score
12,653
Location
California
I have always liked Walker Exhaust OEM replacement mufflers. There is ONE C-body muffler from about 1965 to the 1973 model years. Dual exhausts had the same muffler, just two of them. Talking about 383-440 C-bodies, not sure what the 318 cars had under them. NAPA used to sell Walker Exhaust products under the NAPA name (and the same part number as the Walker items).

There was ONE year where the 440/375 C-bodies had a different muffler, Street Hemi in this case, than the normal muffler. It was the 1969 Polara police car with the 440/375 engine. Other parts of the exhaust system were the same. 1968 and 1970 440/375 cars reverted back to the normal C-body mufflers.

In 1969, the 440/375 police Polara set a top speed record of right at 150mph in the Michigan State Police Car Tests. A record that took a mid-1980s IROC Camaro 5.7L TPI to BARELY best. That particular Polara had a 2.7 rear axle ratio and L84-15 tires on it, for a bit of an overall gearing advantage of the normal 3.2 rear axle ratio, in the top speed area.

The genuine Streeet HEMI mufflers were of the same case sizing, just shorter and with larger inlet and outlet pipes. In that later-1960s time frame, there were only TWO real facctory low-restriction mufflers. The Corvair TURBO mufflers and the Chrysler Street HEMI mufflers. There were MANY imitations, too! The Corvair TURBO dating back to the Corvair Sypder turbo cars of the very early 1960s. So imitaitons of that Corvair muffler was the first use of the term "turbo muffler" in relation to a "performance" muffler, but some were better than others, as some companies wanted a "cheap imitation" to sell lots of them. The OEM Corvair Turbo mufflers were more rounded in the case dimensions, whereas the Chrysler Street HEMI mufflers were flatter, as per normal Chrysler mufflers of that time, and were easier to fit under low-ground clearance vehicles.

What I put under my '67 Newport 383 4bbl car (Chryslers with the 383 4bbl got a factory single exhaust as similar Plymouths and Dodges for dual exhausts) was a "from the y-pipe back" '72 Imperial exhaust system. Seems that THAT application used a normal C-body sized muffler that has very similar flow restriction as the Street HEMI muffler, with 2.5" pipe diameters. It all fit well . . . other than the very rear resonator-eliminator pipe and a simple adapter to the original y-pipe ball joint connection at the very front. My "sewer pipe single exhaust". At the rear, the body contours of the slabs angles upward to the rear bumper whereas the Fuselage C-bodies had a more horizontal line between the rear wheels and the rear bumper. A tweak at the muffler shop, for a slight upward angle fixed that.

In current times, it seems that the ONLY people who like the Flowmasters (the models with the fewest number of internal "flow directors") are the 5.0L Mustang enthusiasts. You can hear them coming, if you know what to listen for!

I believe that if you go into the Walker Exhaust online catalog, you can find the specs for the Chrysler mufflers (as to case size, pipe diameters, and pipe orientations). Walker was an OEM supplier and their stuff was an exact fit for the factory production OEM items. I highly suspect that your car has been "muffler-shop-ized" with a generic muffler of an incorrect length, something they had that "will fit" and is welded to the pipes (rather than using quality exhaust pipe clamps)? By observation, most muffler shops will use a generic muffler of a similar size rather than order in a correct muffler, from my experiences. Nothing really wrong with that, just that what they use is usually not exactly correct. Gets the job done. BTAIM

If not using a Walker Exhaust muffler, then MagnaFlow would be my next choice. Of the correct size and such, of course. And using quality exhaust pipe clamps so that I could change it in my driveway with the car on sturdy jack stands (or on an overhead lift), at least in my younger days. Some muffler shops, around here, were very variable in the quality of the work they did, back then.

Sorry for the length. Just my experiences.
CBODY67

I have a few very low mileage C body Chryslers and Imperials and most of them are single exhaust with resonators in the rear. i have yet to find any aftermarket underfloor muffler, even from Walker or Magnaflow that is even close in dimensions to the relatively large original mufflers on my cars. The original mufflers were quite wide and very long longitudinally. Nothing aftermarket is even close. I would like to see an actual photo of one that is even close to the original ones - they don't exist in the aftermarket anymore as far as I can tell. Even the dual exhaust C bodies I have utilize quite large mufflers and nothing in the aftermarket is even close to them either.

I like my cars to be quiet and I don't like hearing the constant drone of every firing event for miles on end when just cruising - it just hastens fatigue while driving long distances. I don't care much about how loud the exhaust note gets when accelerating hard but when driving normally, the more quiet the better, like most new vehicles. A quiet Chrysler or Imperial also contributes to the feel of a luxury vehicle rather than a usual cheap one. When I look underfloor at some large vehicles with large V8 engines for example like Chevrolet Suburbans, they have large single mufflers that must be 5 feet long underneath the floorpan and you can hardly hear the engine inside the vehicle at any driving conditions other than heavy throttle accelerations. Do I have to go to a Chevrolet dealer and order a factory muffler to get a quiet exhaust these days?

So please show me some photos of any muffler in the aftermarket that even comes close to the dimensions of the original mufflers. Thanks!
 
Last edited:

Boydsdodge

Senior Member
FCBO Gold Member
Joined
May 26, 2020
Messages
1,003
Reaction score
1,380
Location
Toronto Canada
I had good results with the mufflers on my Imperial using muffler made by Motivair. # PF106. I used two of the PF106 mufflers on my TTI dual exhaust.

I found it to be the closest to the specs I found in my old MOPAR/Autopar muffler catalog.
IMG_0315.JPG


IMG_0885.jpeg


IMG_0316.JPG
 

Big_John

Illegitimi non carborundum
FCBO Gold Member
Joined
May 21, 2013
Messages
16,586
Reaction score
22,723
Location
Marcellus, NY
My '70 300 convertible had Flowmasters on it when I bought it. I hated the damn things... As a stopgap, I added some cheap glasspack mufflers in the spot where a resonator would be. That brought it down to an acceptable, but still annoying drone.

I scrapped the system and put a complete TTI system with the Dynomax Super Turbo mufflers. Much better, but after a couple years, it seemed to get louder. I looked at replacing the mufflers with something longer, but while I really like the TTI system, they didn't leave any extra space. Can't go forward because it would hit the floor pan and can't go towards the rear because of where they've bent the pipe to go over the axle. The upsweep happens within a couple inches of the muffler. That really limits my selection. I've been thinking of adding glasspacks again.... Possibly before the mufflers. I can't quite bring myself to taking a sawzall to that TTI system just yet....

Keep in mind, this is a convertible and you hear a lot more of the noise with the top down.

BTW, the "Turbo" muffler was originally designed and built for the early Corvair with the turbocharger. In the 60/70's it was the muffler of choice for performance cars,
 

Trace 300 Hurst

Professional Tinkerer
FCBO Gold Member
Joined
May 27, 2018
Messages
2,054
Reaction score
2,494
Location
Ponte Vedra Beach, FL
BTW, the "Turbo" muffler was originally designed and built for the early Corvair with the turbocharger. In the 60/70's it was the muffler of choice for performance cars,
Indeed, the Corvair muffer (before it was a "turbo" muffler) was designed to provide minimal backpressure against the turbocharger that had already muted most of the roar of exhaust pulsations.

I just recalled that when I was 17-18 (1974) and put headers on my 340 Dart and basically fabbed (poorly) an exhaust system for it, I found some left-over 409 Impala mufflers in the rafters of the garage I was working at. Owner let me have 'em, and man-o-man did those big mufflers sound sweet. They rusted out in a few years and I had to start over (Thrush Hush, maybe?) but it was a good lesson on factory hi-perf cans.
 

HWYCRZR

Senior Member
FCBO Gold Member
Joined
May 13, 2015
Messages
4,613
Reaction score
6,081
Location
Fargo, ND
On my ‘68 383-2 I found a NOS muffler for a reasonable price from a member here and found an NOS resonator on E-bay. The stock sound is a nice quiet burble at idle and quiet at road speeds. I kept the stock single exhaust.
 

saforwardlook

Old Man with a Hat
FCBO Gold Member
Joined
Oct 8, 2011
Messages
7,435
Reaction score
12,653
Location
California
I had good results with the mufflers on my Imperial using muffler made by Motivair. # PF106. I used two of the PF106 mufflers on my TTI dual exhaust.
[/URL][/URL][/URL][/URL]

I found it to be the closest to the specs I found in my old MOPAR/Autopar muffler catalog.View attachment 578021

View attachment 578018

View attachment 578020

This is the first reply to this often posed question by me that really hits the bulls eye. Thank you very much for this new information to me at least. It is just want I was hoping to find somewhere. :thumbsup:

This is also the second Canadian company that I have learned about this month that really impresses me with their offerings/capability - and the owner, Brent, is very capable and easy to communicate with and shows his enthusiasm for making the best mopar products in his field out there (don't let the name fool you as their real capability is so much broader) :

Welcome - Premium Dash Decals by Mr.Heaterbox

I highly recommend them............................
 
Last edited:

Trace 300 Hurst

Professional Tinkerer
FCBO Gold Member
Joined
May 27, 2018
Messages
2,054
Reaction score
2,494
Location
Ponte Vedra Beach, FL
I like mine idling an around town, but it does have a drone at certain speeds. I don't know the exact model, but it is a "turbo" muffler by cherry bomb. I would go quieter now.
The "turbo" thing is fine for modded-up musclecars, IMO. After all, that's where you're going to find 3+ inch diameters--in a strong fully-welded design--to handle 500+ inch engines. But for us CBods....quiet power is the way to go.
 

Boydsdodge

Senior Member
FCBO Gold Member
Joined
May 26, 2020
Messages
1,003
Reaction score
1,380
Location
Toronto Canada
My '70 300 convertible had Flowmasters on it when I bought it. I hated the damn things... As a stopgap, I added some cheap glasspack mufflers in the spot where a resonator would be. That brought it down to an acceptable, but still annoying drone.

I scrapped the system and put a complete TTI system with the Dynomax Super Turbo mufflers. Much better, but after a couple years, it seemed to get louder. I looked at replacing the mufflers with something longer, but while I really like the TTI system, they didn't leave any extra space. Can't go forward because it would hit the floor pan and can't go towards the rear because of where they've bent the pipe to go over the axle. The upsweep happens within a couple inches of the muffler. That really limits my selection. I've been thinking of adding glasspacks again.... Possibly before the mufflers. I can't quite bring myself to taking a sawzall to that TTI system just yet....

Keep in mind, this is a convertible and you hear a lot more of the noise with the top down.

BTW, the "Turbo" muffler was originally designed and built for the early Corvair with the turbocharger. In the 60/70's it was the muffler of choice for performance cars,
I had the length problem you discribe on my Imperial. I had to cut 1.5" from muffler and 2" from tail pipe. Then I used the stainless 2.5" band clamp. Fit and is nice and quiet with flow.
 

Big_John

Illegitimi non carborundum
FCBO Gold Member
Joined
May 21, 2013
Messages
16,586
Reaction score
22,723
Location
Marcellus, NY
I had the length problem you discribe on my Imperial. I had to cut 1.5" from muffler and 2" from tail pipe. Then I used the stainless 2.5" band clamp. Fit and is nice and quiet with flow.
As it sits right now, the front of the muffler body is close to the floor pan (at the kick up for the rear seat) and I wouldn't want it closer. At the rear of the muffler, there's really not enough straight pipe to trim back.

Bottom line is there's really no wiggle room for a longer muffler. I would think that your Imperial probably has a longer wheelbase and a little more room.
 
Top