Yet another 3" exhaust thread...

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Mar 5, 2006 | 10:53 AM

#16

Pkupman82

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From: Muskegon, MI (home)

I'm going to run 2.5" on mine with a 3.5" tip.

Mar 8, 2006 | 01:28 AM

#17

mcne

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Roushians I am wondering the same thing. My stock exhaust on my 1987 F-150 is 3" from the front cat to the second cat. My truck already had full 3" exhaust when I bought it 8 years ago so I am not sure what the stock size after the second cat was. Did stock EFI exhaust go from 3" from cat to cat, then down to 2.5" to the muffler and the rest of the exhaust? I always wanted to ask someone who had stock Ford exhaust.

Mar 8, 2006 | 01:53 AM

#18

Col Flashman

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From: La Verne, California

It sort of looks that way to me, of course that's just from what I've viewed.

Last edited by Col Flashman; Mar 8, 2006 at 01:55 AM.

Mar 8, 2006 | 02:06 AM

#19

optikal illushun

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From: Coal Region

Quote:

Originally Posted by mcne

i think it was 2" from the manifolds to the first cat then 3" from cat to cat then 2.25 out to the muffler and tailpipe...

Mar 8, 2006 | 09:55 AM

#20

thunderb

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Joined: Jun 2003

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From: Lancaster, SC

If the 3" pipes free, try it. If you lose anything, then pay for a smaller diameter exhaust or buy some smaller pipe. Don't worry about theory, just try it, it's free.

Mar 8, 2006 | 10:37 AM

#21

Roushians

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Joined: Jul 2004

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From: Toronto, ON

Quote:

Originally Posted by optikal illushun

i think it was 2" from the manifolds to the first cat then 3" from cat to cat then 2.25 out to the muffler and tailpipe...

I don't know about the 2" from manifold to first cat, but, those observations of the cat to cat diameter and cat -> muffler -> tail are correct

Mar 8, 2006 | 02:00 PM

#22

bchunter

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I am with GHog since I haven't dynoed mine from before to after, but I did not notice any difference in the seat of the pants dyno when I went to 3", but like thunderb said, it was free so I tried it. Then again, I have changed gears so that will change things. All I know is that my check engine light has not come on since I replaced the stripped cats with a high flow one.

Mar 8, 2006 | 02:51 PM

#23

Couinte

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Joined: Aug 2004

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I don’t have a fuel injected engine but I have a the exhaust manifold from one and it’s really 3” in dia. I bought a 3” union and a full 3” dynomax muffler (there is mufflers with 3" in & out tubes that have 2.5" tubing inside) … all that come in front of my rear well in a 45’ angle … works fine and sound great ! (on my 86 f-150, rv cam, 570cfm, dp offy)