[coonhunter70]

I'd like the simplicity of dumping my exhaust at the rear axle right behind the mufflers but I want to remain fairly quiet definitely no drone, What muffler would you use or is this wishful thinking?

[ZeGermanHam]

Have you done this with any other cars? I've been in lots of muscle cars that are set up like this, and I hate it. It causes a lot of cabin noise (regardless of the muffler you choose) because there are open mufflers directly underneath the floor pan. And then there is the fact that you will smell like exhaust fumes after driving your car for 10 minutes. I'd consider this setup for a drag car, but that's it. I've spent enough time in cars where the exhaust dumps at the muffler to know that it sucks.

[george kujanski]

Nope.....don't do it. Wrong on many levels...exhaust and noise getting into the cabin. Did that when I was young and backed out of it within days.

George

[Chris65LeMans]

In high school, those were called “turn downs”. As has been said - they are loud. I spent many a day cruising in one - then had my ears ringing for some time afterwards.

If you want to “remain fairly quiet,” you don’t want to do that.

[coonhunter70]

Years ago I had a 69 firebird setup like this and yes it was loud, louder than I would want today. I was just wondering if anyone knew of a muffler that might control the noise in this situation. I'm not even sure if a stock type muffler wouldn't be too loud?

[b-man]

Carbon monoxide entering the interior of the car is pretty much a given with exhaust exiting under the floor pans, really not a good way to go.

[ZeGermanHam]

This.

Originally Posted by b-man

Carbon monoxide entering the interior of the car is pretty much a given with exhaust exiting under the floor pans, really not a good way to go.

This. Stinking of exhaust and killing a bunch of brain cells gets old really quickly.

[Sprocket]

I ran an axle dump setup in my '70 GTO for years. The pipes were angle to exit roughly behind the rear tire and not just straight over the axle and down. I used Terminator mufflers at the time with headers and 2.5" exhaust. Drone was not an issue, but "remaining fairly quiet" is impossible. For instance, just idling along through a parking garage will set off every car alarm you encounter. Other than that, I loved the sound and fumes in the cabin were a non-issue because of the finish angle of the pipes.

[Bob with the 66]

Originally Posted by ZeGermanHam

Have you done this with any other cars? I've been in lots of muscle cars that are set up like this, and I hate it. It causes a lot of cabin noise (regardless of the muffler you choose) because there are open mufflers directly underneath the floor pan. And then there is the fact that you will smell like exhaust fumes after driving your car for 10 minutes. I'd consider this setup for a drag car, but that's it. I've spent enough time in cars where the exhaust dumps at the muffler to know that it sucks.

I went this route and in my opinion don't even consider this for a street/drag car, the drone, shake, and noise turns the car completely into a drag car. Without a helmet on you don't even want to drive the thing.

[Donovan]

I did this on my 68 FB with a new Pypes system at the time. They sent me 2nd gen tails so I just had the shop put on dumps right after the dynomax turbos.

It sounded amazing especially through the mid-range. But the drone off-idle and the booming at idle got old. I think I drove it on and off for year before getting the right tails in. Tail pipes make an exponential difference in noise level.

Even with quiet 2.5 turbo mufflers it was LOUD. The fact you are asking if it's possible tells me it's the wrong idea for you

I thought it was exhilarating at full throttle!

[Lee]

Maybe if you use some stock Honda Civic mufflers. the sound will be reasonable, You'll lose a LOT of power, but it probably won't be too loud.

[Jack Gifford]

Somewhat related to this topic-
My '37 Buick coupe (Pontiac Tri-Power engine) had glass-packs and short 90 degree tailpipes that came out under the rear of the running boards. No drone, no fumes in car.

[Goatracer1]

The exhaust contains moisture and corrosive acids which will attack the underside of your floor and anything else under there..

[coonhunter70]

Alright thanks for the responses