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Aftermarket mufflers… any favorites?

Started by BeaterGT500, May 02, 2023, 04:50:53 PM

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Putting my 67 GT 500 together with non-stock exhaust (have all correct pieces in storage for later).  Has the 428 with JBA SS tri-Y headers on it.  Planning to run 2.5" pipes with an H or X, stock hanger locations, out the rear valence.  I had a small block car with the old Flowmaster 2 chambers and it was LOUD.  Not shooting for that loud, but want some tone at idle.  Been reading about Magnaflow, and Dynomax.  And favorites out there?
Current custodian of 1967 GT500 #683, and a real Meyers Manx dune buggy. Also currently broke as a result.


Both are good choices. However, be careful, the 'Ultra-Flows' from DynoMax can be a bit loud. Not as noisy as those pesky 2 chamber Flowmasters. Magnaflow's Muscle Car turbos have a nice rumbling mello non drone tone. I suggest a Google/YouTube search and hear them both.
Past owned Shelby's:
1968 GT-350--Gold
1970 GT-500--#3129--Grabber Orange.
Current lifelong projects:
1969 Mustang Fastback/FOX chassis, 5 speed, 4 wheel discs, with a modern Can-Am 494 (Boss 429), Kaase heads, intake with a 1425 cfm 'B' Autolite Inline carb, ala Trans-Am style
1968/70 Olds 442 W-30


Spin Tech's are my favorite. Running them on my CJ Mach with H pipe. Previously ran them on a 427 in a 68 GT 500 with full 3" exhaust, Tri Y headers, and Dr Gas X pipe. I'm going to duplicate that exhaust on my 427 Fairlane.
1965 G.T. 350
1967 Fairlane GT - 482 4-speed
1970 Mach 1 - 428CJ 4-speed/AC
1971 Mach 1 - 429CJ auto/AC
2005 Ford GT

Royce Peterson

I am not impressed by the Flowmaster 2 chamber mufflers at all. I put some on my car in 1994. By 2004 one of the baffles came loose so I replaced both mufflers with new ones. In 2014 one of the baffles came loose again. This time I got replacement mufflers from Midas guaranteed forever.
1968 Cougar XR-7 GT-E 427 Side Oiler C6 3.50 Detroit Locker
1968 1/2 Cougar XR-7 428CJ Ram Air C6 3.91 Traction Lock


The 3 chamber Flowmasters on one of my cars are 34 years old and I never had a problem with them. I had 2 chamber Flowmasters on 1 of my cars and they were fine. A little loud but I didn't mind. I have 3 chamber Delta Flow Flowmasters on 2 other cars and my pickup truck. I love the sound and they are not too loud at all.
68 1/2 CJ Mustang GT FB auto 3.91s 68 1/2 CJ Torino GT FB 3.91s 60 Thunderbird 64 Falcon Sprint conv. 4Spd 65 Falcon Sedan Delivery 67 Fairlane 500 SW 428 4Spd, 68 Torino 4dr 95 Thunderbird SC. 89 F250 Supercab 2wd, 98 Mustang conv. 99 Jeep Cherokee 2002 Thunderbird. 96 Harley FLSTN Heritage Special


I never had any issue with the FlowMaster 3-chamber on the car I had for over 20 years, and they were not as loud as the 2-chamber, good sound and very livable.
'67 Shelby Headlight Bucket Grommets
'67 Shelby Lower Grille Edge Protective Strip


Dynomax Super Turbo were perfect on my old 428 CJ Torino.  Not loud or droning at cruise but nice sound on throttle.


Does anyone have the Dynomax Super Turbo on a small block?  I have a 347 Stroker motor in my carryover and I have two chamber Flow master and they sound great but are to loud with way way to much drone.  I am trying to decide between three chamber FM or maybe try the Dynomax.  Getting rid of the drone is my main priority


Quote from: JD on May 03, 2023, 06:57:24 AM
I never had any issue with the FlowMaster 3-chamber on the car I had for over 20 years, and they were not as loud as the 2-chamber, good sound and very livable.

There was no drone on what I had, Tri-Y headers, 2-1/4 inch pipe, 289 bored "30-over", aluminum heads.
'67 Shelby Headlight Bucket Grommets
'67 Shelby Lower Grille Edge Protective Strip


Have FlowMaster Delta-40 2-chambers on my 66 with a 347, sound great and really liked it ~20 years ago when I installed them but way too loud for me now. I'm looking for the same recommendations as OP.
Dave - 6S1757


6S554 Family owed since May 15,1974. Confirmed original alum T-10 4spd, MICO,

SPF 0373 Cobra S/C, Shelby alum 488 stroker FE Tunnel Port, TKO


I am going to suggest Magnaflow 15816 2.5" system. Complete system. I have a similar system (but 3") on my 69, it is top quality and a great sound. Stainless, mandrel bent system. Includes X pipe. I am very happy with the fit, you would probably have to get an exhaust shop to modify the tail pipes to go thru the valance, but I installed the rest of it at home.

fwiw Mike

TA Coupe

I started with Flowmaster single chamber, then 2 chamber and finally 3 chamber and It never changed very much inside but it's not bad outside. Had a friend blast by at full throttle and I was very surprised how nice it sounded.

If it starts it's streetable.
Overkill is just enough.


Turbo-style mufflers have always been the "go To" muffler design. I had them on both the 68 302 and the 69 428 SCJ. Great tone, quiet until you hit it hard, and then still good.