Ok, I already have a single exit 2.5 glasspack on the truck...I noticed that where the Y-pipe and the pipe off that one are welded, it blowing thru...not much yet. but Ive noticed it slowly getting worse. And wow is that y-pipe small lol. So I would like to go with true duals...84 250 T19 6.9 2wd, so I dont have to worry about a tcase. Now my questions are How big of a diameter should I go? I was thinking 3 or 3.5 inch would be good, Its still an N/A truck, i would like to turbo it one day..but that it way down the road. And I love the sound of the IDIs straight piped. so my other question is...will it be ok to run that size of diameter pipe with no mufflers? I had a friends dad who is very mechinacally inclined. But is a Chevy guy tell me that it needs backpressure, you cant run it with out a muffler.... But I know some of you on here have em this way. Now im not gonna say he is an unintelligent fool...he does know some stuff, He just a Chevy guy who drives Fords....Anywho, If yall could lemme know whats good. Id really appriciate it. Thanks!

 

IMHO the more free flowing the better, and opening up that intake can take full advantage ot those big tubes your going to have.

 

Iv'e been running straight pipe for over a year. no problems so far. she seems to like it...... i have one of the loudest trucks in town..... everybody knows when im coming iv'e been told lol

 

Thanks for the quick reply 84...And I concur with you. I will also be making a custom CAI for it...I figured 420 cubic inches would really like to breathe much easier. But this guy went on this thing about Diesels need backpressure or youll trash the motor. Like I said, this is a Chevy guy telling me how to fix my and/or make my Fords faster. i respect his opinions since he is my buddies dad. but I take his info with a grain of salt. Also is trying to convince me that I need a $800-something Barry Grant 750 race carb for my 9.5:1 358w 93 octane running BRONCO...

 

1994 how big are yours? And thanks for the reply, I figured that it would be fine, but my buddy's dad was getting quite frantic about keeping a muffler on it or else "Kaboom!" didnt exactly tell me what kaboom was or could be. so I just wanted to know. thanks again!

 

My 86 is straight piped didn't have any issues that was caused by that

 

I'm sure that someone else will jump in with it but I heard the technical description of why these engines don't need any backpressure (as opposed to gasoline engines).
It had something to do with valves IIRC, buit don't quote me.

I had always heard that backpressure is really important with gas engines but not on ours, and then recently someone had the tech details on it. Anyways, open er' up!
I have the 3.5" Banks, I figure they have it pretty well tuned so 3.5" is probably plenty.

 

3.5" seems to be the most commonly used. Big enough for airflow, but not so loud you'll get hate letters. 4" w/ a turbo though apparently is the sweet spot. If your gonna keep it n/a 3.5", if turbo is in your future, go 4".

 

If you are going to run true duals 2 1/2 is plenty as your restriction will be at the manifolds.

And no you dont need any backpressure on a diesel, any diesel that I know of. Some semi's run straight a million miles or more.

straight pipes on a non turbo are loud, they sound real sweet at low rpm's, but at a certain rpm especially when loaded, it gets unbearable.

 

Thanks Everyone for the quick replies and knowledge. I figured backpressure really wasnt a concern with these motors. when I was installing the Glasspack, i Fired it up for abit just to hear it. and It sounded grea. I figured Id be safe instead of sorry and throw something on it. But, I think Ill prolly end up goin with 3 in. nice in the middle of the road size. And when I do go to Turbo it, Im going to pull the motor out and "freshen" Her up for it. Do it Right the 1st time ya know? lol Again, Thanks for all the insight and opinions. When I go to get it done, Ill be sure to update about it

 

When mine was n/a with straight stacks anything over 2100rpm was unbearable.... probably something to do with how the pipes were tuned.

As far as the glasspack, i've heard that diesel will plug it up fairly quickly, then you'll be left with just another piece of pipe. Might look into flow through diesel mufflers...

 

I agree I spent many hours on a John Deere 4230 with a strait pipe on a baler, nothing worse then a loud noise with a pulse.
And 2x on the strait through muffler, soot from these critters can sometimes plug regular mufflers up.

 

Interesting, I didnt think of the soot. Well, In light of this info, I may look into the "diesel" mufflers then. I do like loud pipes lol. But the neighborhood might appriciate the break haha
Anyone have any recommendations?

 

I had a 10" stack on ol red and she sounded monstorous at over 2k. but maybe because it was so unrestricted =X i loved it, going for dual 4" now...
-Dalton

 

Too...too much lol...