I will probably run HP exhaust manifolds on my 440 Challenger. The car will be approx a 450HP car with the modifications. Like everyone else I want my system to flow optimally but without alot of drone.

I do place a value on a relatively quiet system without giving up alot of flow. Ive been reading most of the exhaust system posts and find them interesting. Ive seen guys do the following with their cars.

Now assuming HP stock exhausts...

1. Running mufflers under the floorpans and then straight thru exhausts over the axle and out the back.

2. Running no mufflers under the floorboard but some kind of long muffler where the resonators would have been after the axle.

3. Running mufflers under the floorboard "and" mufflers of some kind where the resonators would have been. Does this quieten the system down that much more and does it restrict the system that much more.

I like my car to have that relatively quiet sound cruising but expect the drone when I put the pedal to the floor. I just dont want that loud sound where it crowds out my radio.

I kind of like the muffler and resonator system as it looks generally correct in appearance, but not at the expense of alot of restriction.

Im happy to hear from your experiences.

I cant add any more than what I put on the nearby lengthy ex thread but I am a firm believer in X pipe setups along w resonators along side the rear springs in addition to dynomax muffs. Yes pri tube dia/length is important and the link states collector dia/length is also & I believe that any dia reduction from the header collector flange rearward (starting w collector reducers) costs power though the 1 guy said he went from 3" tailpipes to 2&1/2" & lost virtually nothing.

i agree with the use of an X-pipe to make that extra bit of power. but,with 450hp,honestly,a mild 440, 3" exhaust is complete and utter overkill. 2 1/2" is more than adequate,with dynomax ultraflows and round,canisiter style resonators at the rear,will offer a nice mellow,deep,yet non-johnny-law-dawg-attracting sound.

I used "Accurrate Exhaust" on my car [69' runner] with stock exhaust manifolds. I used their over the axle pipe instead of resonators, which it should have.

The car is very quiet. No droning,vibrating, ect. I too wondered about performance loss at the time, but am very happy with results, looks, sounds, performance, ect.

The car goes low 13's 1/4 mile @ 104 mph.

My goals were not maximum performance, so I was [and still am] O.K. with leaving some perf. on the table. It is worth the driveability aspect of it for me

As you already know, you will need to decide on looks, sound levels, performance goals, originality, ect.

Happy decision making!!

At a show I heard a car with only mufflers near the rear where the resonators originally would have been. It sounded very good to me. But I wonder if there would be alot of drone if these were the only mufflers on the car?

I have 4 mufflers, 3-1/2" system, incl x-pipe, over the axle, 2-1/4 TTI's into 4" collector.
Room was an issue. Not sure of the sound yet, but hoping 4 x magnaflows will quiet it a little..

I have always wanted to run a "stock" type exhaust.
I would consider 2.5 mandrel bent tubing with an x-pipe,Dynomax super turbo(hemi,i.e. long case)with 2.5 tailpipes with some stainless magnaflow mufflers(smaller diameter ones with a round case that look like a resonator),and stock tailpipes.
Overkill?Sure but it would be cool and sound great!Albeit EXPENSIVE.

At 450 hp, you don't need anything larger than 2.5". Mine has Ultraflows. It is fairly quiet under a lot of operating conditions. But cruising from about 1800 to 2100 rpm, it drones. Unfortunately, with my gear ratio, I spend considerable time in this rpm range.

BTW, on e-bodies the round cans behind the axle Are the mufflers, the resonator are the ones under the floor pan.

I value quiet also and I could not get it with 3". My 528 Hemi uses TTI 2.5 " with an X pipe and the super turbo mufflers. It has a nice low tone during normal cruise and sounds very good on the throttle. The X pipe really makes a big difference and I believe it helps eliminate the drone that I had with basically the same system in 3" with an H pipe. With your hp, you would be fine with 2.5", Dave Dudek advised me that 2.5 would work well with mine and he runs 2.5 with manifolds on his FAST Hemi car.