Exhaust/Muffler?

Stock muffler dimensions:
2" ID inlet/outlet, 16-3/4" length body, 22" overall length, 2-1/2" length inlet, 2-3/4" length outlet, 4-1/4" x 8-3/4" oval body. Offset inlet/center outlet

Walker Dynomax # 18107 for '71 to '74 applications (freeflow exhaust)
Summit Racing Part Number:WLK-18107

UPC: 086387181075
Muffler Material: Steel
Case Shape: Oval
Inlet Diameter (in): 2.250 in.
Inlet Quantity: One
Inlet Location: Offset
Outlet Diameter (in): 2.000 in.
Outlet Quantity: One
Outlet Location: Center
Internal Construction: Perforated tube
Muffler Finish: Aluminized
Case Exterior Length (in.): 18.000 in.
Overall Length (in): 22.750 in.
Thickness (in): 4.250 in.
Width (in):

Couple of thoughts.

-First of all, the sound of the muffler will be different from car to car. You can get a general idea, but minor differences in pipe length, diameter, cam, headers/free flows, etc. will potentially change things. A good friend of mine liked the sound of my car and got nearly identical mufflers. They sounded terrible with a drone. The drone is a resonance that can be in the pipes, car body, etc. Just ask a pipe organ maker about pipes and resonance! You can ask as many questions as you like and watch as many youtube videos as you want, but the final proof of how it sounds on your car is going to be installing it.

-Second thing to consider is that turbo type mufflers or any other three chamber mufflers are not generally performance items. Some are better than others, but they are basically an oem compromise between sound, restriction and cost. When I replaced mine with an identical set of straight through Magnaflows I gained an actual measured .4 of a second in the quarter mile with not so much as a jetting change. Any straight through design is going to be A) louder and B) MUCH less restrictive.

Chris   

The only real difference between a glass pack and a Magnaflow is the size of the case. A glass pack gives a couple of inches of packing around a perforated pipe. Magnaflows give a much larger chamber, which will tend to lower the tone if not the noise volume. This will make them less tinny and "rappy" sounding, but I would not place any money on less decibels! The only other thing is I would expect a Magnaflow to last longer with a welded steel body and generally more robust construction.

Chris

I suspect that they pipes and mufflers you had were overkill for the car, particularly on the Hornet, so you had some margin. Losing a bit of flow was not going to make much difference. Also, it is a bit harder to feel a difference at the top end where the benefit is, I am talking measured improvements on a certified track, not the butt dyno.

The most restrictive part of the exhaust will determine the potential flow of the system. If it is the muffler, so be it. If it is the pipes, fair enough.

In my case, the pipes were about right, but the mufflers were clearly the sticking point. If the pipes were not right, there would have been little performance gain from a muffler change. It actually began to pop a bit on a downshift due to lack of back pressure with the new mufflers.

Chris

PS: The mufflers were Walker oe replacements that came off.