What size exhaust are you guys runnin?

[abadsvt]

I am making provisions in my frame for the exhaust and was curious on what size exhaust tube you guys are runnin. I was debating between 2 1/2 and 3". I would prefer 2 1/2 exhaust because i would be able to bend it myself but wasn't sure if 2 1/2 is too small. I am using a LS1 motor with a few upgraded extras and possibly twin turbos if i can afford them. Thanks for the help. Josh

[SactoJim]

I've been pondering the same question.

I found this online and copied....

Basically, as a rule of thumb, if your intended use is strictly street, for cruising and maybe as an everyday driver, then 2.5" will be adequate,,,,,,,,,, unless you have 500 HP or more! For the strip, if you have a power plant rated around 425 or more realistic horsepower, then the 3" system would be the way to go. Powerplants with few horses just will not benefit from the larger 3" exhaust although 3" tailpipes showing from behind the rear wheel or under the bumper will make quite an impression. It's been our experience that too big a system will not hurt performance (as long as the primary tubes on the headers are not too large -- Headers do the main 'tuning' of the exhaust), just cost a little more. Now, how about 3.5"? This Huge size is reserved for the really serious,,,,,,, say 600 horses or more!

If you're not sure of the horsepower rating of your powerplant, but have raced at the dragstrip, then any 1/4 mile ET's in the 12.40 - 12.70 range or quicker would benefit from the larger 3" exhaust versus a good 2.5" mandrel bent system.

With powerplants in this horsepower range or up to 575, with a 3" system, you will be able to basically turn ET's equivalent to those with open headers. Imagine! Running through the exhaust and turning low 11's while your competitor is struggling with all the noise and just trying to keep up.

Most 525 HP or so powerplants will never know the difference between 2.5" or 3" on the street for daily driving or cruising, although the big 3" "sewer Pipe" will certainly look great!

Now, IF you're in the 575 HP area, the Big 3.5" pipes might be your ticket. These are some really HUGE pipes and we've had reports of guys loosing their arms in them....just kidding!

The Following Tech Tips are courtesy of the Dynomax Division of Walker/Tenneco web site. This info can be found here at www.dynomax.com/techsupport.stm.

[chevy72blu]

for a mild to moderate LS1... I'd go 2.5. In my experience, LS1's actually like a little backpressure. Most modern engines seem to be designed this way.

[69heavychevy]

well if you do decide to run turbos, remember that less backpressure=more efficient turbo.

[jim zag]

I use 2.5 inch because it is easier to fabricate out of easy to get pieces. I also have noticed that cars with 3 inch exhaust have a much louder sound and interior noise level. I drive my truck as much as possible and do not like a lot of noise! If you can bend your own pipes you are much better off!
BUILD IT TO DRIVE!

[1970cstblazer]

The truck has dual 2.5" pipes.

[orange72c10]

The articles that I have read say in order to run 3 inch you need to have a lot of hp to make it worth the extra money. I would say to run 2.5 inch for your set up. I have 2.5 inch with flowmasters and am very happy.

[abadsvt]

Thanks for the help guys!!!! I guess i need to figure out if i am going to run the turbos or not. Also what mufflers do you guys recommend. I was hoping for those long skinny ones since i only have about 7" in width to fit the mufflers. Thanks again.

Josh

[SCOTI]

An LS1 would work well w/a mandrel 2.5" exhaust using an 'X' style crossover tube for better scavenging (sp?). You could also do a 3" system from the collectors to the muffler inlets but use 2.5" for outlets/tail-pipes. Regardless... use a crossover if power is important.

[space]

2.5 with 40 series.

[jkade]

ls1, mac mids, 2.5" and h-pipe

[chev74]

do the 2.5" with flows. I reccommend the new Super 44s or the original 40 series. They sound the best. Classic tone, deep sound. The long skinny ones you speak of- do you mean glass packs? or the racing mufflers?

[abadsvt]

Originally Posted by chev74

do the 2.5" with flows. I reccommend the new Super 44s or the original 40 series. They sound the best. Classic tone, deep sound. The long skinny ones you speak of- do you mean glass packs? or the racing mufflers?

I was hoping to use something like these. http://www.magnaflow.com/02product/s...ne=main&id=351 . When i designed all the internal bracing in my frame i got a little carried away so there isn't too much room. In a few days i will have some pics to help everyone understand. I hope these round ones still sound good. Thanks Josh

[chev74]

go for it, I have heard lots of guys like the magnaflows. I personally have never heard them in front of me, only sound clips, and they never do justice. I am SURE they will sound great

[Ackattack]

I have 2.5" dual with X pipe in my corvette (LS1) and it seems to do well. It's making about 350RWHP.

My 72 GMC (TPI 350) has 2.5" duals (no X pipe) that is not mandrel bent.

For my 68 Chevy, I'll be running 3" mandrel bent. I'm hoping for 400RWHP. It's going to be a bracket racer/show truck so noise level isn't a big concern.

Oh, and just for reference the LS1 F-bodies run a 3" single pipe back to the muffler, and they're doing fine, so 2.5" duals should be sufficient for most applications.

[abadsvt]

Do you guys think i will need an "X" pipe?

[bad6772]

when mine was together i ran 3 inch from the manifolds to a cross over then 3 inch to the mufflers( flowmaster 40 series) then 2.5 for about a foot and then a turn down...

[Ackattack]

an X pipe will help make more power. It will also help to tone the noise down a little too.

[bad6772]

i meant a x pipe sorry

[corn]

2 1/2 will be perfect. Plenty really. The X pipe will improve low end torque & quiet the low RPM tone too. I dont run them though...

[abadsvt]

Thanks everyone! I am not quite ready to install the exhaust but now i have a game plan!

Josh

[jkade]

Originally Posted by abadsvt

I was hoping to use something like these. http://www.magnaflow.com/02product/s...ne=main&id=351 . When i designed all the internal bracing in my frame i got a little carried away so there isn't too much room. In a few days i will have some pics to help everyone understand. I hope these round ones still sound good. Thanks Josh

You will like them, they sound like nothing I have ever heard. I have them on my 67 with the ls1 and I will also put a set on my blazer with the 6.0 If I knew how to make a good quality sound clip I would. You can't go wrong with them and summit had the best price at the time.

[Slammed70]

Originally Posted by chevy72blu

for a mild to moderate LS1... I'd go 2.5. In my experience, LS1's actually like a little backpressure. Most modern engines seem to be designed this way.

In my Camaro....I ran Kooks headers with a 3.5in primary, into a Mufflex 4in Y-pipe and 4in through to the back where there was a Dynomax Bullet muffler, then Y'd off into dual 3in over the axle and out the back.

[WinDancer]

I made the decision to run full headers even though I had to raise the truck for clearance.
I also made the decision to run full 3 inch headers and full 3 inch straight out the back with 3 inch flowmasters and crossover tube.
If you have ever stood behind a full 3" dual exhaust and listened to it idle and run hard you will know exactly why some of us spend the extra $$. NOTHING else sounds like it.
So what you need and what you want can be two very different things It all depends on you and what you want from your truck.
Good luck with your decisions.

[Mondo]

A single 3in will flow the same as dual 21/2in. I think it sounds better too (smoother).... just don't use a flowmaster unless you like your sound loud, low, and with truck vibrations thrown in (experience).

Windancer, they must hear you coming for miles