Exhaust for 5.7L vortec?

DanMan_S · August 1, 2003

I've done alot of searching among these forums and such but I haven't been able to find much information on modifying the exhaust on a '98 GMC sierra with a 5.7L vortec as compared to '99 or newer a 5.3L or a 6.0L. I've got a extended cab '98 sierra Z71, and really want to put a more aggressive sounding muffler on it with some nice dual tips. I was focusing on getting a Flowmaster 50 series dual inlet/ dual outlet and then have the tips cut out behind the rear tires at 45 degree angles instead of straight sideways. I want the 50 series, because I don't want the obnoxious noise of the 40 but still want to make a bold statement. Does anyone have any comments on their success or failure with using a flowmaster behind a late model 350? Is there any major power loss issues I should consider, or is it a pretty safe mod if I just cut the old muffler out and throw in a new one with the dual tips? Any thoughts would be great.

ridnlow · August 1, 2003

I have used 40 series on all of our vehicles and i love the sound... I have the 5.7l in my tahoe with the pipes exiting out the sides and i can hear it when i get on it but not when im cruising on the interstate.. what an improvment from my old truck with straight pipes.. boy that gets annoying..

Jersey Tahoe LT · August 1, 2003

Ridnlow. Do you have Dula Mufflers or dual in dual out?

Later,

Brandon

ridnlow · August 1, 2003

I messed up and bought Single in Dual out muffler.. so the muffler shop had to make a Y pipe to make it to Single in Dual out.. if i was gonna keep the truck i was gonna sale this muffler and get a dual in dual out.. but im selling it so who cares. it still sounds awesome..

DanMan_S · August 2, 2003

How's the power of the truck after adding the muffler? Any improvements? Also, how bad is the 40 series for waking up the neighbour hood? I live in a cul-de-sac, and routinely pull burnouts and donuts...plus usually leave really early in the morning and come back late at night. Will my neighbours be looking to kick my ass in a hurry?

Anyone had any experience with the 50's on the 5.7L? Are they still pretty noisy, or are they barely noticable from the outside?

ridnlow · August 2, 2003

My neighbors dont even know im leaving .. and the power isnt a big difference but its aight.. i just love the sound.. i like to know when im pressing the gas

99-2door · August 2, 2003

I have 2 forty series on my 97 Sierra and I love it. My 99 Tahoe has a dual inlet, dual out muffler that sounds awesome. I am not sure what series it is, I lucked out and the first owner had had the system installed. The great thing about the 5.7L vortec is that it has 2 cats and all you have to do is install 2 mufflers and the rest of the pipe and you have a TRUE dual system with an awesome sound.

DanMan_S · August 2, 2003

Wow, geez, you guys pretty much got me convinced to get the 40's. So, there are no significant or noticable power losses that I'd have to worry about with switching to the flowmaster with dual outlets?

greyghost03 · August 2, 2003

Wow, geez, you guys pretty much got me convinced to get the 40's. So, there are no significant or noticable power losses that I'd have to worry about with switching to the flowmaster with dual outlets?

I love my Flowmaster 40! Single in dual out - no power loss and great sound!

Just make sure the outlet pipes are 2.25". The 2.5" pipes are a little big and may cause you to lose a little low end torque.

Huntaholic · August 2, 2003

40 series delta flow flowmaster here too! I love it! I dont know which one was responsible for it, but when I put the flowmaster and a K&N air filter in I picked up almost 2 MPG! This is on a 98 5.7 vortec too by the way.

99-2door · August 3, 2003

I love my Flowmaster 40! Single in dual out - no power loss and great sound!

Hey greyghost,

does the 4.8L have a single exhuast inlet to the muffler from the factory? I know the 5.0L only had one. I wonder if GM did this on the smaller V8s in order to gain some torque over the true dual system the 5.7L and 5.3L have. Any thoughts?

greyghost03 · August 3, 2003

I love my Flowmaster 40! Single in dual out - no power loss and great sound!

Hey greyghost,

does the 4.8L have a single exhuast inlet to the muffler from the factory? I know the 5.0L only had one. I wonder if GM did this on the smaller V8s in order to gain some torque over the true dual system the 5.7L and 5.3L have. Any thoughts?

Yes.

From the headers there are 2 cats going into a y-pipe which converts it to a 3" pipe to the muffler.

I don't know if it was set up in this way to gain low-end torque or maybe to even save $$$ but it works! This setup would provide a little more back-pressure. I didn't notice any loss when I had the Flowmaster installed, even w/the dual outlets!

96 Vortec · August 3, 2003

I used the "American Thunder" cat-back system from Flowmaster on my truck. Bolted up real easy with the help of a friend and some cold beers. Very nice tone, added low end torque and the system comes with stainless steel pipes at the end so there are no "tips" to add to make the pipes look big or shiney.

Bulldog · August 4, 2003

I'm seriously looking at the FLO-17317 setup from Summit. It's a single-in dual-out setup with 3" tips. Should bolt up nicely to my truck. The only question I have but haven't heard back from Summit yet is what muffler comes with this kit? Waiting to hear back.

DanMan_S · August 9, 2003

I've been doing some checking into the issue, and saw that I don't want to replumb the exhaust inorder to put dual 40 series mufflers in. So I'm settled on getting a dual in/ dual out 50 series SUV muffler, with side exiting tips. That should be the simplest for now. What inlet and outlet sizes are recommended for hte best power outta that 5.7L vortec?