Possible Exhaust Idea:

DenaliHD66

Original poster
Member
Dec 4, 2011
597
1. I'm going to be putting my new exhaust manifold on soon, its a Dorman OE replacement one. The casting is rough around the ports and I was thinking about getting a dremel and smoothing them out. Would it hurt to port these out a bit to open it up, or would that cause compression losses?

2. Also, my current exhaust setup is OE cat converter, 2.75" piping to a 2.5" inlet/outlet flomaster muffler, and then 2.75" OE piping to the rear hanger and (the tip fell off) so that's where it stops.

3. My muffler has a dent in it and is pretty rusty/rattles around, and I was thinking about just straight piping it from the cat (Ideas for a good high flow cat?) and all the way out the back with a stainless tip. Would this work out well? I would have to test out the sound to determine whether or not I liked it.

My current setup is probably due for an entire replacement by now anyway, so I'm looking for an inexpensive solution but something that will last the rest of my truck's lifetime. Thoughts, ideas? I don't mind being a semi-guinea pig for this one.
 

oh05ext

Member
Dec 7, 2011
166
ive always wondered if i could make the exhaust off a 1500 silverado work as it doesnt squish down over the axle and possibly exit better out the rear
 

oh05ext

Member
Dec 7, 2011
166
According to the walker book at work the trucks with the 6.0l and diesel's both have a 3" exhaust
 

Showtyme

Member
Nov 26, 2012
150
Its your truck so do what you want but i think it will sound like garbage with no muffler. I would at least throw a cheap glasspack in there but you'll probably still get snap crackle pop when you let off the gas pedal.
Edit Im on my phone so idk what engine you have. If you have the v8 it wouldnt sound nearly as bad as the I6.
 

DenaliHD66

Original poster
Member
Dec 4, 2011
597
Nope, its the 4.2L. If I had the V8, I would have already gone all-out with a nice system. Okay, so maybe a muffler, but is 3" piping too large? I just don't like on my current setup how it goes down to 2.5" inlet/outlet in the muffler. I feel it would restrict the flow a bit.
 

Playsinsnow

Member
Nov 17, 2012
9,727
Want to make sure your exhaust is not too free flowing and has some back pressure. I've read many threads in old forum (banned can't link em, sorry!) that compare I6 aftermarket exhaust to ricer sounds, not enough pressure at the end. A little reading.


http://gmtnation.com/f25/new-member-exhaust-opinion-3187/


http://gmtnation.com/f26/exhaust-3592/

Some folks seem happy with a cat back exhaust, or even two mufflers. Might love the sound initially-but may become too much for comfort after a few hours on the road. My .02.
 

Showtyme

Member
Nov 26, 2012
150
DenaliHD66 said:
Nope, its the 4.2L. If I had the V8, I would have already gone all-out with a nice system. Okay, so maybe a muffler, but is 3" piping too large? I just don't like on my current setup how it goes down to 2.5" inlet/outlet in the muffler. I feel it would restrict the flow a bit.

Idk how much difference 3" vs 2.75" is gonna be. If your looking for max flow then obviously the 3" would be better but you probably wont pick up any extra hp. Im not sure but i think these engines like a little bit of back pressure. You might throw a code if go 3" straight out.
 

Ryda55555

Member
Apr 11, 2013
1,111
The previous owner was a dummy and put 3" all the way back no cats or mufflers and it was STUPID LOUD and would not suggest it
I threw in a normal cat and then 2.75 to a magnaflow muffler and 2.75 to a magnaflow 4" tip and it sounded amazing when you got on and had a lot of snapping and popping sounds which i liked but the drone killed me
So i threw a thrush turbo muffler where the resonator is supposed to be and it made it a very mellow growl but when it heats up it still drones
About a week ago i noticed my cat was rattling bad probably because i ran the truck with a bad thermostat for too long
So im going to put a magnaflow high flow cat in and hopefully thats what cause a lot of the drone but either way it'll add alot more popping and snapping to the tone without being too loud

You should check out conekilrautoXs exhaust system, it sounds amazing

But i suggest going with either the dynomax or thrush as they arent too loud but gives a nice tone
For some reason i've heard 4.2 i6s with magnaflows and flowmasters are drone monsters
Or you could always go with the corsa kit but its pretty pricey

Edit: 3" piping with no cats or mufflers was really slow on the low end
Heres a little pointer- from what i've learned from alot of mechanics is that cars needing back pressure is not necessarily true and is only half right
An exhaust system is like a person blowing through a hose
If the hose is too big you cant have a constant flow because you empty your lungs too fast and you get tired which is bad
If the hose is too small you have to put too much force to blow out and causes pressure at the source (engine) which can cause ruptures
So what the ideal size is going to be is whatever your truck can push out at a nice steady constant pace
 

gmcman

Member
Dec 12, 2011
4,658
Here's an idea I have been toying with, would either sound like complete crap or may have potential...dunno but kinda pricey to try at the moment. Something along the lines of splitting after the cat with a Cherry Bomb, then two Flowmaster, then back to either a single or dual Vibrant resonators. The three mufflers should fit inside the factory muffler location.
 

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