Suggestion and why...

[Andy4639]

What size exhaust should I run? They hooked the old 1 1/2" back up to the headers for now to get it running. I talked to a guy Thursday and he gave me a price of $430.00 out the door with Mega flow mufflers, x pipe with flanges so if I need to work on it I can remove it. 2" aluminium pipe made in Canada and ran to back of the truck with no tips as I plan to have it dump at the rear staright down.
Should I wait until I get the exhaust done before tuning it?

[littlevictories]

i've gone 2.5" minimum on all my rides and been happy. Had 3" mandrel bent stuff on a big block car, sounded awesome.

currently running 2.5" non-mandrel x-pipe kit from summit and magnaflow XL's

love it, super mellow and quiet. no death drones or brown notes.

but I am getting old and listen to black metal at reasonable volumes now

[ls1nova71]

I've never had anything smaller than 2" on a V8, are you sure you have 1 1/2? Your TPI probably would have run better with something a little bigger. But anyway, on a realitivly stock LQ4, I would go at a minimum of 2 1/4, but definitley wouldn't hurt to go 2 1/2, as that's what I usually run. Also, I'm sure its aluminized steel pipe and not aluminum.

[BR3W CITY]

I wouldn't run 2" unless it was a stock-swap, and I was doing a fairly non-restrictive true dual. No reason not to go 2.5", as most of the aftermarket mufflers are going to have an input of 2.5-3" The piping doesn't cost much more, but the flow difference is signifigant, especially when considering that you gain the .5" volume on either side.

2.5 or 3, don't go bigger unless you've got a hairdryer under the hood I haven't seen.

[Andy4639]

Yes it is aluminized steel pipe and not aluminum. That's what I meant. OK then 2.25" minuim. I will stop by again and see what he says about it. No hairdryer under the hood and it's just a stock 6.0 with headers.

[crazy longhorn]

Go 2 1/2" , on a true dual....add an H or X pipe to the system. Muffs, your choice, as well as "dump em @ the axle, or rear exit? Do you want to here it, or do you want the rest of the world to here it? Dump it, or exit ahead of the wheels, for you....for the rest of the world, run the duals straight out back? Be prepaired, to spend some coin in that shop, for a sweet job! Longhorn

[Andy4639]

The exhaust will run to the backside of the rear axle then dump straight down. No chrome tips, nothing fancy at this point!

[lolife99]

"Dumps" straight at the ground will not make you any friends at the car shows.
This will create alot of dirt and dust on your truck and others that are close by.
At least dump them at a 45 degree angle or out the side.

[Andy4639]

Originally Posted by lolife99

"Dumps" straight at the ground will not make you any friends at the car shows.
This will create alot of dirt and dust on your truck and others that are close by.
At least dump them at a 45 degree angle or out the side.

Hadn't thought about that. I will have to rethink on this now!

[BR3W CITY]

Dumping straight down will also echo it off the ground, meaning that the sound vibrations get transferred straight down. The "rattle" this creates pisses people off. Even at lower Db levels. At one point I was ticketed for my old exhaust "feeling too loud"....go figure. Despite the ticket being written like crap, its sorta true.

[cableguy0]

You want 2.5 inch pipe. Also get some name brand mufflers the cheapies do not last. Mega flow is a knock off. I prefer flowmaster myself. A 6.0 had 2.5 inch y pipe into a 3 inch pipe factory. If you want it to breathe it needs to have dual 2.5s. Anything less is not enough. Keep in mind a single 3 inch pipe flows more than 2 2.25 pipes.

[crazy longhorn]

I run 50 series Flow masters on mine....awesome sound on my 5.3 ! She does run 2 1/2 " pipe, front to rear, H pipe & exit out the rear. Also the Magna flow muffs are very nice...I would go for the 18" body on the muffler...this will give a nice mellow note while cruising, but you will hear it , when you kick the loud peddle! Resonance is lower on the 50's flows, as compaired to the 40's ...(nicer to cruise on the road), but they still "kick" on the sound at WOT ....Longhorn

[85burb]

2.5 would be the minimum I would ever consider again. I had 2.25 duels and they sucked. sounded very bad and didn't flow very good. now have duel 3 inch mandrel with super 40s. sounds way better. Flows great. A bit over kill but I will never need more exhaust.

[Andy4639]

Well for those of you who don't know me personally. I wear hearing aids. Both ears. I don't want the flowmasters since all I've heard about them is that they are loud even at idle. With my hearing aids if it's as loud as I have herd them and people say I want be able to hear anything other than the exhaust and that want work. I want it to be quiet enough to talk and listen to the radio when driving. I don't want to wake the hood up when I leave out either, like some do on their Harley's around here. That's another story though. If you look at the pictures you see I have dauls on it now, just not big enough for what size motor I have now. 2.5" all the way back and see what to do once he gets it installed and see how to make it exit.

[Dustytrix]

Thats what I would do , all the way out the back. I had 45 turned towards the wheels before the rear and it was loud. Now its out the back and I can enjoy the hiway.

[BR3W CITY]

Originally Posted by cableguy0

Keep in mind a single 3 inch pipe flows more than 2 2.25 pipes.

*Straight pipe can/will flow about 115cfm per square inch of area on the cross section of the pipe.

a 2.25" pipe would flow an est 408cfm per pipe, so leaving out stuff like xpipes, thats ~816cfm of flow.

A 3" pipe by the same math would be 747cfm.

*the constant and equation were made by people smarter than myself.

[Custom 68]

Andy I like the Magnaflow, they are straight thru and really dampen the sounds. I had flowmaster knockoffs for a while with an H pipe and they had a drone I didn't like. I think a 2 1/2 setup is what you would want also.
I now have the turbo and a single magnaflow and it sounds good to me.
As far as tuning it yes I think for a final tune you will want the final exhaust on it. It will make a difference. I know some even say going to headers from manifolds will change it. I assume these guys are going to do a street tune for you? They should be able to swap their wide band o2 sensor for one of yours and turn yours off for the tuning and get you a real nice tune that is responsive not just at wide open throttle.

[Andy4639]

Originally Posted by Custom 68

Andy I like the Magnaflow, they are straight thru and really dampen the sounds. I had flowmaster knockoffs for a while with an H pipe and they had a drone I didn't like. I think a 2 1/2 setup is what you would want also.
I now have the turbo and a single magnaflow and it sounds good to me.
As far as tuning it yes I think for a final tune you will want the final exhaust on it. It will make a difference. I know some even say going to headers from manifolds will change it. I assume these guys are going to do a street tune for you? They should be able to swap their wide band o2 sensor for one of yours and turn yours off for the tuning and get you a real nice tune that is responsive not just at wide open throttle.

Thanks, This is what I was hoping to do. I don't really care for the wide open tune since it's going to be a street truck. I will talk to Bruce and see what he thinks and yes I think I will have the exhaust done before they do the final tune.

[Billett]

I have a stock 6.0 with headers as well. Custom exhaust with 2.5" mandrel bent all the way out the rear cost me $400 including an x-pipe and welding in cut-outs. Mufflers and cut-outs were bought separately. I went with hooker aero chambers and may never get anything else. They are very quiet around town with a pleasant rumble you feel more than hear but at WOT on a 6.0 it sounds mean as hell. Like the magna flows you can see right through them when you have em in your hands, just a lot of baffling packed in there.

2.5" is a good size for stock/mild v8s. The crush bends also kill some of the flow so think of them as closer to 2.25" mandrel tubes. However on a stock motor its a great size to increase the scavenging effect of a crossover pipe. Too much pipe = too little exhaust velocity, too little pipe = excess back pressure. NO BACK PRESSURE IS GOOD! Don't listen to people who say "you need a little bit."

Edit: before someone jumps on me; pressure is used in exhaust to tune the pulses of exhaust to increase scavaging from the cylinder, but that is not back pressure, that is creating a low pressure area outside of the cylinder at the correct TIME. Not purposefully increasing pressure in general.

[Andy4639]

From what the muffler guy said all bends are mandrel so want loose anything there. I'm going to find out who Bruce recommends also for this before I do anything. he told me he had a local guy that does it but didn't give a name yet. It maybe the same guy.

[Billett]

Even better then. Personally I think if you really like a deeper tone you can do whatever size exhaust you want. If you go 4" mandrel you will definitely be robbing HP for sound, but hey if it's a show car just for fun, then I say whatever floats your boat, but if you are looking to DD or for performance than 2.5" mandrel is probably your best bet. It leaves you some room for upgrades, but isn't TOO big right off the bat. 2.25" might gain a few HP, but then you have to redo the whole thing when you upgrade. And we always upgrade

[BigRed76]

On my 5.3 swap I went with 2.5" true duals with aluminized pipe and an x-pipe. I bought universal mandrel bent pieces and routed/welded the exhaust myself to get exactly what I wanted. As far as mufflers I used two magnaflows that are 24" long with a 5"x 8" body, and then turndowns right in front of the rear axle. The great thing about magnaflows is they are a straight thru muffler so you loose no power like with the flowmasters, but they still do a great job of muffling the sound.

Honestly it turned out quieter than I wanted, I probably could've used an 18" muffler and liked it, but it still sounds awesome at higher rpms. At idle it sounds like a big block and at cruising speeds its pretty mellow, not a problem to talk to other people or hear the radio, and I have no insulation in my cab.

[Andy4639]

Talked to Bruce Friday. I gave him the info that the muffler guy told me. he said his guy would beat that price. He said if nothing else just to get me to let him do it since bruce is doing the work on the truck. He is suppose to LMK something Wensday.