Yet another 3" exhaust thread...
Thread Starter
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Tuned
Joined: Aug 2004
Posts: 311
Likes: 4
From: Omaha, NE
Yet another 3" exhaust thread...
My buddy is going to give me a 7' chuck of 3" pipe, I figured not to let it go to waste. I have a painfully bone stock 4.9 (EFI) with some serious rusted and busted exhaust (let’s just say the exhaust comes out the front of the muffler more than the back...).
So my point is not should I put it on, I have enough free time to warrant the installation, but more so should I be looking for a muffler too? Hadn't planned on it since I’m broke, but I can't stand overly loud exhaust either.
Planned on chopping the second cat, and run a reducer down to the stock pipe and run the whole 7 feet back. Maybe get a turndown tip.
Any tips/scoldings are welcome.
So my point is not should I put it on, I have enough free time to warrant the installation, but more so should I be looking for a muffler too? Hadn't planned on it since I’m broke, but I can't stand overly loud exhaust either.
Planned on chopping the second cat, and run a reducer down to the stock pipe and run the whole 7 feet back. Maybe get a turndown tip.
Any tips/scoldings are welcome.
Senior User
Joined: Feb 2006
Posts: 227
Likes: 0
From: Paulding County
Originally Posted by fattmann
My buddy is going to give me a 7' chuck of 3" pipe, I figured not to let it go to waste. I have a painfully bone stock 4.9 (EFI) with some serious rusted and busted exhaust (let’s just say the exhaust comes out the front of the muffler more than the back...).
So my point is not should I put it on, I have enough free time to warrant the installation, but more so should I be looking for a muffler too? Hadn't planned on it since I’m broke, but I can't stand overly loud exhaust either.
Planned on chopping the second cat, and run a reducer down to the stock pipe and run the whole 7 feet back. Maybe get a turndown tip.
Any tips/scoldings are welcome.
So my point is not should I put it on, I have enough free time to warrant the installation, but more so should I be looking for a muffler too? Hadn't planned on it since I’m broke, but I can't stand overly loud exhaust either.
Planned on chopping the second cat, and run a reducer down to the stock pipe and run the whole 7 feet back. Maybe get a turndown tip.
Any tips/scoldings are welcome.
Elder User
Joined: Mar 2004
Posts: 784
Likes: 0
I had a spare 3" from my diesel and put in on my truck. I put a flowmaster collecter (two to one) then a highflow cat, then the left over exhaust that had a Flowmaster 50 on it already. I notice no difference in power, but it doesn't bark as loud as I would like it, but hey, it was already paid for. I had to reroute my second 02 sensor to go in behind the cat. I say go for it if you can make it work. There are a ton of mufflers out there that I am sure you will find one you like.
Thread Starter
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Tuned
Joined: Aug 2004
Posts: 311
Likes: 4
From: Omaha, NE
Well it's on an 87 van, haven't done any mocking up yet, so not sure about fitting issues.
Probably looking to get a Walker downpipe down the road, so that should help.
You mentioned a second O2 sensor, are there really two? Only noticed the one, but haven't really studied the exhaust yet.
Thanks for the words of advice, will be sure to check that length clearance before buying anything else.
Probably looking to get a Walker downpipe down the road, so that should help.
You mentioned a second O2 sensor, are there really two? Only noticed the one, but haven't really studied the exhaust yet.
Thanks for the words of advice, will be sure to check that length clearance before buying anything else.
Thread Starter
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Tuned
Joined: Aug 2004
Posts: 311
Likes: 4
From: Omaha, NE
And why is it too large? Not saying your views aren't wrong, or anything, just looking for your reasoning.
The pipe is free, that's my rational. I would tell GHog that 4" is too big, but he seems to love it.
Do you not like the sound of 3" or are you coming from a more mechanical aspect in that it is in fact detrimental to the performance? Just looking to get all sides and learn a few things (not very keen on the exhaust area).
The pipe is free, that's my rational. I would tell GHog that 4" is too big, but he seems to love it.
Do you not like the sound of 3" or are you coming from a more mechanical aspect in that it is in fact detrimental to the performance? Just looking to get all sides and learn a few things (not very keen on the exhaust area).
Postmaster
Joined: Mar 2002
Posts: 3,545
Likes: 4
From: Coal Region
Generally an increase of exhaust size of one step is ok, per say stock on out EFI 300s is 2.25, so moving up to 2.5 is ok.
going to 3" u will slow down the exhaust gas velocity to much, loosing low end torque. u have to think of an exhaust system like a complete system. it all needs to be "tuned" for the engine and thought out right. throwing anything larger than a single 2.5" pipe on a stock 300 is silly. and ghogs 4" stack is just down right ludicris, but he likes it so thats cool.
only when a 300 is built up to move enough air to make the 2.5" exhaust a bottle neck is when u run into trouble and that is usually when the head is ported, large cam is used or in a boosted application.
going to 3" u will slow down the exhaust gas velocity to much, loosing low end torque. u have to think of an exhaust system like a complete system. it all needs to be "tuned" for the engine and thought out right. throwing anything larger than a single 2.5" pipe on a stock 300 is silly. and ghogs 4" stack is just down right ludicris, but he likes it so thats cool.
only when a 300 is built up to move enough air to make the 2.5" exhaust a bottle neck is when u run into trouble and that is usually when the head is ported, large cam is used or in a boosted application.
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Tuned
Joined: Aug 2004
Posts: 311
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From: Omaha, NE
I see, good points.
So I guess my next question would be- am I going to lose and noticable performace from the 3"? Not planning on doing any pulls in the near future, or building the motor (being broke sucks). Just the everyday hauls (heavy wood, furniture, illegal immigrants, etc).
So I guess my next question would be- am I going to lose and noticable performace from the 3"? Not planning on doing any pulls in the near future, or building the motor (being broke sucks). Just the everyday hauls (heavy wood, furniture, illegal immigrants, etc).
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Postmaster
Joined: Mar 2002
Posts: 3,545
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From: Coal Region
from talking with a friend who had 3" exhaust on his truck, he said didnt notice a loss but he went to 2.5 then and said it felt strnger so i would say u will loose some.
oh and its not im hauling illegals, its about hauling magic elves. i run a company that delivers magic elves to different jobs...they work cheaper and understand the jobs better.
oh and its not im hauling illegals, its about hauling magic elves. i run a company that delivers magic elves to different jobs...they work cheaper and understand the jobs better.
Thread Starter
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Tuned
Joined: Aug 2004
Posts: 311
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From: Omaha, NE
Hmm, well I guess that'd good to know, and I've been wasting all this time evading customs officers!
Well like I said the 3" is free, and figured I'll use it. When I get around to doing full exhaust, the proper way, I'll keep your comments in mind and maybe give you a ring.
Thanks a bunch, all of you!
Well like I said the 3" is free, and figured I'll use it. When I get around to doing full exhaust, the proper way, I'll keep your comments in mind and maybe give you a ring.
Thanks a bunch, all of you!
Senior User
Joined: Sep 2003
Posts: 310
Likes: 1
Originally Posted by fattmann
The pipe is free, that's my rational. I would tell GHog that 4" is too big, but he seems to love it.
Having never had the truck on a dyno, all I can go by is seat of the pants and it certainly doesn't feel like I've lost anything with the 4" pipe.
I'm trying to set up a pull but I'm having problems finding anyone who wants to hook right now.
I've got about 2 months before any organized pulls start, hopefully I can find a victim before then.
Postmaster
Joined: Feb 2003
Posts: 3,441
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From: Muskegon, MI (home)
Originally Posted by GHog
Having never had the truck on a dyno, all I can go by is seat of the pants and it certainly doesn't feel like I've lost anything with the 4" pipe.
I'm trying to set up a pull but I'm having problems finding anyone who wants to hook right now.
I've got about 2 months before any organized pulls start, hopefully I can find a victim before then.
I'm trying to set up a pull but I'm having problems finding anyone who wants to hook right now.
I've got about 2 months before any organized pulls start, hopefully I can find a victim before then.
MMMM Cummins Power 
the possibilities!
Elder User
Joined: Jul 2004
Posts: 620
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From: Toronto, ON
Hmm.. I have a 96 with the 4.9L I-6. Now, I measured the diameter of the pipe between the first and second cat, and it is indeed 3". So i was going to cut off the exhaust at the beginning of the 2nd cat (leaving the air injection and o2 sensor), and do 3" piping to the back.
Now I'm not sure what to do (listening to those good points made about backpressure)
Now I'm not sure what to do (listening to those good points made about backpressure)