N/a single 5 inch straight pipe ?

[heavyhauling]

As some of you already know im putting a 1991 7.3L in a 1980 international S2125 5 ton truck. I want to make a single 5" straight pipe from the manifolds out to the 5" chrome exhaust stack, it will be roughly 12 feet of pipe including the single stack. I will be making my own intake system and throwing the stock air cleaner set up in the scrap pile. This is all temporary till I get a turbo and intercooler.

My question is, do these motors need any exhaust back pressure to run properly ?

 

[redneckaggie]

I dont have any and mine runs fine. My system is y pipe, about a ft of 3 in into 4in all the way back to an 8 in tip.

 

[mattplumber]

Just a forewarning- a non turbo truck with a straight pipe and a stack will be very loud and irritating. Its kinda like running with open headers. The increase in pipe diameter alone will open up power, but without a muffler of some sort just be prepared to keep a bottle of aspirin or advil in your glovebox for the headaches you will get from the drone of the stack behind your head. Its even worse for a passenger.
My experience is from reg cab trucks only, crew cabs might be less harsh on the ear drums i would think.
Straight pipes and stacks are only meant to be run off turbos in my opinion..........

 

[OLDBULL8]

Sungi mungi chikey chikey ungi alligany fungi oooh. That's Chinese for, where the hell is all that noise coming from.

 

[CDX825]

No back pressure needed with these monsters!

 

[tractorman86]

No back pressure needed with these monsters!

+1 there, it will be a bit loud but try it out and see if you like it. It will be easy to splice a muffler in if it is too loud

 

[gonecrazyi]

Im use to running open headers or stacks on bb dodge motors and the idis don't compare for being loud unless you are wrapping them out. I have 3 in pipe running to the back of the truck and its quite with the window up and loud with it down. It *** dumping under the cab for over 2 years but that got rediculous plus the whole underside is covered with sooot now lol.

 

[BlueBreadTruck]

When I did my N/A setup, I used a 3" flowmaster then stepped up as I went through the bed. sounds good, but not too loud

 

[heavyhauling]

do you guys think Ill gain any power with this exhaust and intake set up with absolutely no restriction ?

 

[FordGuy100]

Yes you will gain some power. Probably the best thing it will do will be to help EGT's. Might be able to turn the pump up some.

 

[6.9poweredscout]

I had 5" pipe after the Y pipe on my 250, it sounded good and wasn't too loud, but that was under it dumping in front of the rear tire. I turned the pump up and the truck really ran strong! Id do it.

-Jon

 

[Agnem]

I think we have pretty much concluded that there is improvement up to a 3.5" pipe, but beyond that, it's for looks or sound. You will loose stack velocity with too large a pipe, and your smoke will just waft out instead of fly decently. Yes, this will be VERY loud.

 

[f-two-fiddy]

I think we have pretty much concluded that there is improvement up to a 3.5" pipe, but beyond that, it's for looks or sound. You will loose stack velocity with too large a pipe, and your smoke will just waft out instead of fly decently. Yes, this will be VERY loud.

The Gail Banks memorial library pretty much confirms that. I'll take His word for it over any back yard engineer.

 

[heavyhauling]

It don't matter how loud its going to be, we will never drive this truck in a well populated area. The only reason I want to use this size of pipe is because I have the stacks already and they are in excelent condition. They might not be exacly 5" it might be 4-4.5". Ill go see later on.