New exhaust yes or no.

I had a 1994 chevy K1500 with the 5.7 350 small block. I loved the truck in every way, but the exhaust was just too quiet for me. I had a muffler shop install a flowmaster single in/dual out to the bumper. Sounded great, like a whole different truck. There wasn't much drone at all. I got rear ended and the exhaust got all bent up, so I had to get the two pipes past the muffler replaced. I put them at an angle past the rear tire, sort of at a 45 degree angle, and had larger tips installed. Then, the truck sounded AWESOME. It had a very deep tone, I used to love driving that truck with the windows down.

I replaced the exhaust on my diesel because it had a MASSIVE hole rusted through it. Once I informed my wife of the MASSIVE hole, she had no problem with me spending the cash to replace it with something with much more flow potential.

Here is a picture of that massive rust hole: :B :W


Here is a view through the muffler that replaced it:


Installed:


Overall, it is noisier (especially under hard acceleration), and around 2200 RPM - 2400 RPM. When cruising, there is no drone at all, but that ~2300 RPM range does have drone/noise.

The system is 4" mandrel bent aluminized steel, made by MBRP, and shipped to my door was about ~$300.

BurbMan wrote:
Sccotsk, like I said the Flo-Pro 2506 and a few others in the Big Oval series are direct replacements. They have different volume levels, if you;re not sure, email Flo Pro tech support, they are very helpful.

The muffler is a weird set up....it looks like it's dual 3" in and dual 3" out, but the outlets come together in a Y into a single 3" tailpipe. If you look at the muffler off of the vehicle, there is only ONE 3" outlet, the other is a dummy pipe there to act as a helmholz resonator.

Wow, I did not realize it was a dummy pipe. That's why it's so hard to find. Thanks for the info.

Sccotsk, like I said the Flo-Pro 2506 and a few others in the Big Oval series are direct replacements. They have different volume levels, if you;re not sure, email Flo Pro tech support, they are very helpful.

The muffler is a weird set up....it looks like it's dual 3" in and dual 3" out, but the outlets come together in a Y into a single 3" tailpipe. If you look at the muffler off of the vehicle, there is only ONE 3" outlet, the other is a dummy pipe there to act as a helmholz resonator.

8.1 big cast stainless manifolds, it has two 3" pipes all the way back to the muffler, two 3" out and into a 3.5" single tailpipe... Truck's not turning 9000 rpm, that stock exhaust is plenty unless you got money to throw away, if so save a little for a good set of ear plugs...

Mine has two inlets and two outlets to a 3" tail pipe. Having a hard time finding the replacement. That's why I was thinking cat back. I'll stick with stock exhaust as per all of our directions. Does anyone know of a two inlet/outlet direct bolt in replacement?

BurbMan wrote:
Save your money....I did a LOT of research on the exhaust, and if you call Banks, they will tell you that they don't even make an aftermarket kit for the 8.1 (except on the Workhorse chassis) because the stock exhaust on the 8.1 trucks is VERY efficient. The 8.1 may the only, or least one of only a few, big block gassers where there are NO performance gains to be had from a "cold air" intake or "performance" exhaust. If you look at the airbox on the 8.1, it already takes cold air from outside the engine compartment. The exhaust is 3" duals with separate cats that flow into a single muffler, then connect to a single 3" tailpipe.

I am not an exhaust expert, but from the research I've done, changing the exhaust may provide HP gains at WOT, but may actually cause you to LOSE low-end torque, which is the opposite of what you want in a TV.

I needed a muffler this year (hole rusted in it from too much Montauk beach camping LOL) and was going to go Magnaflow, but the local exhaust shop told me straight up that he couldn't guarantee it wouldn't drone. I wound up with the Flo-Pro 2506, it's a direct fit for the OEM. Cost me $150 for the muffler and another $150 to have it welded in at the shop.

Very happy so far, sounds and performs like stock, which in my view is a good thing....changing up the exhaust on these big blocks is more likely to cause problems than produce any benefits. Loud mufflers sound cool around town, but when you're on a long RV road trip cruising for hours at 65-70 MPH, the last thing you want is to hear your muffler....

This is the prevailing wisdom. The 8.1 is factory tuned to work with the exhaust it has. If you install a free-er flowing exhaust without a tune, you will lose torque and mpg under the exact conditions we use. How much you will lose depends on lots of factors. Since the 496 has tons of torque to start with, you may not notice much difference. If you want it louder, go for it. Just don't expect any gains anywhere else unless you're willing to go full boat as some others have posted.

ls1mike wrote:
There is plenty that can be done with exhaust and intakes on EFI modern engines. Look at the Ford MOD Motors and LSX motors. My own 11 Sec 1/4 LS1 Trans Am is a good example. The difference between an LS6 intake on an LS1 is about 15 to 20 HP at the wheels without a tune.
Next you do the tune and get even more gains. The best way to do it is on the Dyno.

Now having said that a catback alone won't do it. You may see a few hp at the wheels, but you won't even notice it and you will be out at least 500 bucks.

A complete exhuast system with a tune on a modern EFI vehicle may net anywhere from 20 to 40 RWHP depending on the engine and type of exhaust system.

My WS6 gained 26 HP and 32 FT/LBS of toruqe from a custom exhaust, stock cats and mid length headers. Then with the LS6 intake I picked up another 16 hp and 13 ft/lbs of torque. All at the wheels, Dyno proven.

Problem is you have to be willing to do the whole thing. Headers, Cats, exhuast and tune. So you are looking at a pretty good chunk of money. 1200 bucks for nice headers, 300 bucks for a dyno tune and at least 600 for a complete custom exhaust. More if you get an off the shelf catback.

If you are not trying to pick up tenths in the 1/4 mile, I am not sure it is really worth it unless you like the sound.

It is why my 6.0 Chevy truck, which is really similar to the 5.7 in my WS6 is bone stock minus a tune to change the Transmission shift points and when the torque converter locks up.

Nice car!

To the op, leave it alone until it falls off, then pick something nice. Performance or mileage won't be worth the cost.

If your pipes need to be replaced, I'd get Magnaflow 15716. Otherwise, I'd get a Magnaflow stainless muffler of the same size as stock.

Save your money....I did a LOT of research on the exhaust, and if you call Banks, they will tell you that they don't even make an aftermarket kit for the 8.1 (except on the Workhorse chassis) because the stock exhaust on the 8.1 trucks is VERY efficient. The 8.1 may the only, or least one of only a few, big block gassers where there are NO performance gains to be had from a "cold air" intake or "performance" exhaust. If you look at the airbox on the 8.1, it already takes cold air from outside the engine compartment. The exhaust is 3" duals with separate cats that flow into a single muffler, then connect to a single 3" tailpipe.

I am not an exhaust expert, but from the research I've done, changing the exhaust may provide HP gains at WOT, but may actually cause you to LOSE low-end torque, which is the opposite of what you want in a TV.

I needed a muffler this year (hole rusted in it from too much Montauk beach camping LOL) and was going to go Magnaflow, but the local exhaust shop told me straight up that he couldn't guarantee it wouldn't drone. I wound up with the Flo-Pro 2506, it's a direct fit for the OEM. Cost me $150 for the muffler and another $150 to have it welded in at the shop.

Very happy so far, sounds and performs like stock, which in my view is a good thing....changing up the exhaust on these big blocks is more likely to cause problems than produce any benefits. Loud mufflers sound cool around town, but when you're on a long RV road trip cruising for hours at 65-70 MPH, the last thing you want is to hear your muffler....