Performance Exhaust Question
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Junior User
Joined: Jan 2008
Posts: 59
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Performance Exhaust Question
Hi there,
I have a 78 f250 4x4 c6 with a mild build new 400 I want to put a good performance exhaust that is loud. I plan to put headers and then i need advice on pipe size. I was thinking 2.5 from the headers into one muffler (flowmaster 44 series) then a single pipe that exits out behind the right tire with a large five inch tip. Would four inches be way to big? I figured thats about what a dual exhaust with 2.5 pipe would equal or a little more.
Thanks
Alex Hunt
I have a 78 f250 4x4 c6 with a mild build new 400 I want to put a good performance exhaust that is loud. I plan to put headers and then i need advice on pipe size. I was thinking 2.5 from the headers into one muffler (flowmaster 44 series) then a single pipe that exits out behind the right tire with a large five inch tip. Would four inches be way to big? I figured thats about what a dual exhaust with 2.5 pipe would equal or a little more.
Thanks
Alex Hunt
Post Fiend
Joined: Apr 2008
Posts: 8,261
Likes: 15
From: Big Sky Country
Running a single exhaust defeats the purpose of running headers, which is to decrease back pressure, promote exhaust scavaging and increase exhaust velocity, i'd advise running at least a true dual exhaust or even true duals with an X crossover pipe about one foot behind behind the headers collecters, personally i'd save your money on the flowmasters and run a quality set of 3" diameter by 24" to 30" long perforated core (not louvered core) glasspacks right off a set of long tube headers and run 3" pipe exiting behind your tires with 45's.
Elder User
Joined: Nov 2003
Posts: 778
Likes: 2
From: southeast Idaho
Montana is correct on the muffler he mentioned, but 2.5 should be all you need all the way to the back or where ever you end them, but by all means go 3 if you are concerned, I don't think it will hurt anything, I run 2.5 pipe and 3" glass packs behind my 460 and it has no problems breathing, ran them straight out the back, and I run headers also.. the crossover tube is a good idea too.
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
That's not at all true, a well designed single will work as good as duals on these trucks considering there is no way to run a balanced dual exhaust with the transfer case, front driveshaft, and in some cases a gas tank in the way. I have a system with longtubes, mendrel bent 2.5" Y pipes dumping into a 3" single with a cat and Flowmaster 50 series and it's LOUD, I had a Super44 on there and it was even louder.
Logistics Pro
Joined: May 2003
Posts: 4,238
Likes: 21
From: Northern Illinois
Bigger is not always better. You want to have some kind of back pressure. 2 1/2" is plenty big enough.
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Post Fiend
Joined: Apr 2008
Posts: 8,261
Likes: 15
From: Big Sky Country
That's simply just not true, why would you want any back pressure at all? what you want is exhaust velocity to create a scavaging effect in the cylinders, back pressure is the very antithesis to this.
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Cargo Master
Joined: Mar 2008
Posts: 2,409
Likes: 1
From: Goliad, Texas
my buddy has a 8.1 chevy with dual super 44s no cats......
dual exhaust is always louder than single......no question about it.
Alex, if you want advice listen to montana_highboy and UTfball68, they know what they're talking about.
Post Fiend
Joined: Apr 2008
Posts: 8,261
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From: Big Sky Country
The myth of exhaust backpressure - My Pro Street
Mountain Pass
Joined: Jan 2005
Posts: 141
Likes: 0
An internal Combustion engine needs a minimum of 3% of backpressure to run properly. That being said I would wager that just straight pipe would give at least 3% backpressure and be plenty loud. I have Dual 2 1/4" straight pipe dumped in front of the rear axle on my truck It is loud. But you can be quiet enough to sneak around if you like to. On the duals vs. single topic go to any good exhaust hotrod shop and they will tell you that the single is more beneficial in equalizing the exhaust pressures between the banks of cylinders If you run duals you should at least run an equalizer pipe if you are serious about making power. It will also keep the duals from sounding to different from each other.
Post Fiend
Joined: Apr 2008
Posts: 8,261
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From: Big Sky Country
For the exact reason that the article stated...too much restriction results in the same problem as too much flow. It's fine to stand by your point, but the "proof" that you put out there contradicted itself, and even said the same thing that everyone I've ever talked to has said. Read the third post in the article YOU posted, it equates the exhaust system to a garden hose, you don't want that stuff dribbling out, you want the exhaust to go flying out. I don't get how you can stand by a point that corrects itself in the same article. Just remember next time you post something to read it all or otherwise you look pretty silly using it as backup.
Post Fiend
Joined: Apr 2008
Posts: 8,261
Likes: 15
From: Big Sky Country
Well if you did read the article please tell me why you're using it as your reference for saying that backpressure is bad, when in the last post it clearly states that it is good? I do see in the first 2 articles where it says backpressure on a 4 banger isn't as good, but then the third says the complete opposite, hence it contradicts itself. Look up contradict in the dictionary...you'll figure out what it means. And as far as the garden hose goes...the smaller the diameter the faster the water comes out (more backpressure), the bigger the hose, less velocity (the dribbling I was talking about). It's fine if you believe in what you do, but it's obviously false (proven by your article). The exhaust gases are hot, so to increase performance you want to get the "hotness" out of your system as quickly as possible, agreed? The pressure that is in a smaller diameter pipe causes the gases to move faster and escape out of the tail pipe, agreed? But if you go too big the gases are just fumbling around, with minimal forces behind it to get it out of the system, agreed? However go to small and you'll also restrict flow. Hence the reason most stock-moderate builds should go no bigger than 2.5" pipes. Please feel free to disagree, but do it with proof. I have already blown major holes through your theory numerous times, please tell me what you disagree with in my statements (that are followed with "agreed" since it seems you have an issue with reading the entirety of posts).
