Correct Downpipe Size and Correct Alignment

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Sep 20, 2004 | 11:19 PM

PAN

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From: Hamburg, IL

Correct Downpipe Size and Correct Alignment

I have a 2004 6.0L without a resonated downpipe. The stock one is 3inch i take it correct? I'd like to put on a 4inch but don't know how well if will fit. Will a 3 1/2 inch do just as good as a 4inch? I doubt it. I'm worried the 4inch wil rub the firewall. What about the 3 1/2 rubbing the firewall?

Sep 21, 2004 | 07:05 AM

jdadamsjr

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the 3.5 inch will fit...
have heard that the 4 inch will fit too if installed properly...
worst case scenario is that you have to bend the seam on the passenger side engine bay to allow no rattling clearance when the engine torques...
some used a small jack between the engine/tranny and the seam to push it out...

I don't think you will be able to tell the difference between a manderal bend 3.5 that goes into the 4 inch exhaust from the downpipe back verses a 4 inch downpipe..

I have the 3.5 dp that goes into the 4 inch exhaust and - seat of the pants -
my guess ? 20 to 25 HP increase and 250 degree drop in EGT's from just that....

AND the great sound is a plus....

Sep 21, 2004 | 12:50 PM

PAN

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From: Hamburg, IL

I have the stock downpipe with the stock exhaust tubing minus the converter and muffler. I cut them out witha sawz all and replaced them both with 3 1/2 pipe and a 6inch stainless tip from ITP. EGT's have dropped but from what I have read on here and from other owners, 3.5 or 4 inch down pipe and 4 inch mandrel bent exhaust will lower it another 200 degrees. I found a cheaper dual exhaust kit for anyone wanting duals. Its at www.exhaustproslinc.com/dieselsystems.html. Its a aluminized system that sells for around $450. So does anyone here think that the 4inch will benefit me over the 3.5 at all? What about you tim? The entire system when complete will consist of a either the 3.5 or 4inch downpipe followed by 4inch mandrel bent duals. No mufflers and no cats.

THanks
Paul

Sep 21, 2004 | 01:59 PM

ninelives 59

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From: tampa florida

The 4 inch will not rub the firewall.You just have to adjust it before clamping it down at the turbo.I have a 4 inch down pipe on mine and I have about half an inch of space with the bigger pipe.

Sep 21, 2004 | 08:56 PM

plasterer

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From: elkton

hey
i have four inch all the way back and no rub or bending of fire wall... the 4 inch down pipe went in easier than the three 1/2 came out!!!!!! i guess all the insulation...i didn't reinstall the cat it sounds better than stock(quieter) and when you open it up it sounds like a built gasser.. love it. i tried the no muffler on stock but it was too loud for my neighbors at 530 am.
max
03 250 sc 4x4 banks six gun water/meth 305 bfg's

Sep 21, 2004 | 09:18 PM

PAN

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From: Hamburg, IL

Plasterer,

I have a six gun with speed loader in my truck too. Do you notice when you turn it up on six that if you have modified exhaust it totally changes the sound?

Sep 22, 2004 | 08:42 AM

plasterer

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From: elkton

pan
the exhaust i have is from banks the 4 inch monster. the exhaust just opens up real nice. i wouldn't want to be back there when i hammer it down!!!! it does get a little loud when i get on it but at normal driving it's nice and quiet.they don't know what hit em till your by.. love it
max