Gus,
there is a 6" round Ultra Flow that is 30" long, part # 17299, 3" I/O. I'm not sure if that case is too large in diameter.

In oval mufflers there is an Ultra Flow welded muffler, part #17235, 24" long case, 3" I/O side/center. Body is 4-1/4" x 9-3/4".

That's all I could find in my Dynomax catalog.

What is it going under? Also, do you have room to run multiple mufflers - 2 per side? You can run multiple Ultra Flows & knock-out more noise without hurting backpressure. Also, do you want stainless or is aluminized construction OK?

Eric they are going under my 64 Savoy.I seen a set under a Daytona over at B/E&A Restorations that came with the 3" flowmaster system that looked really nice.I would rather stay with one long large oval muffler if at all possible.
Gus

Free air flow is not the same as high pressure exhaust flow that has pressure pulses behind it so you have to take advertized numbers as what they are....advertisements. Behind each pulse is a vaccuum wave...which left to itself is Filled (equalized) by atmospheric air pressure 14.7psi at sea level,

A true scintific means to demonstrate back-pressure that might be detrimental to the performance of the engine would be to measure the pressure increase against the muffler CASE as engine RPM increases. In all cases heat is absorbed into the exhaust system and velocity drops to the point where the pressure wave equalizes with ambient air pressure (again 14.7psi) where it meats thew outside air. Itf the exhaust flow was indeed RESTRICTED from passing fast enough to satisfy the discharge of the motor, the back pressure would register as an increase in case pressure since the passing air can't get out of the muffler as fast as it's coming in. I suspect the pressure measurements /extremese you would read on most well-designed low restriction high flow systems are nowhere near as dramatic as many people might think....a lot of heat energy is dissipated from the system before it ever reaches the muffler...temperatures drop substantially from ~1800-2000 F at the exhaust valve by the time they reach the tailpipes on a full exhaust car those Chrysler engineers were pretty clever took full advantage of that dissipation of energy by dropping the tailpipe size vs the headpipe and many subsequent tests have proved this as well.

The muffler is only one component of the system, and all a muffler is is a compromise between sound and performance. But that said I'd venture to bet that you have to accept a lot more DB's of sound for a relatively small amount of 'net-net' enhancement of performance. If Feeling and Sounding faster ALWAYS MEANT faster there wouldn't be nearly as many PITA hondas and Harleys making lots of noise and yet not accelerating any faster than my wife's poor little CR-V from a stoplight

WIZE - even the engineers at Dynomax don't talk like that!

Gus, here's my recommendation:

Run a pair of Ultra Flow Welded #17233 (20" bodied), or #17235 (24" bodied). Depends on what will fit under the back seat area. I can build you a pair of 4" diameter resonators for extra noise control at the rear if you have room. The longer they are, the more noise they will knock out. They will have 3" necks & cores, plus a GOOD quality fiberglass packing that will not blow out. I can build them in any length - up to 40" long.

The car you saw with the TTI system was probably running Super Turbos #17793's or 17769's. I have a buddy with a '70 Challenger 440+6 that is running those in his TTI system. The packing blankets broke-down in the mufflers & now the car is hideously loud - TOO loud! Heck, my 3" chambered mufflers would be quieter than those now.

-Eric

I've got Flowmaster 40 series mufflers on my Fifth Avenue with a 9.5:1, Eddie headed 360. The exhaust is 2.5" with cutouts under the doors. Honestly, I can't feel any bit of a difference in power with the car when going through the mufflers compared to the cutouts. The motor should be good (never had it on a dyno) for 380HP. Now the drone, well, that's another issue.