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Discussion Starter #1
I won't do this anytime soon due to low budget but my question is would there be much difference in power/flow if I put on aftermarket highflow catalytic converters with lets say a flowmaster cat back setup with a 40 sereis muffler as apposed to true duals with two 40 series mufflers.
 

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Not if its sized right. I have a 3" single setup on my 91 and its pretty nice. I know that the single has better scavenging to help pull the exhaust out of the ports, is cheaper to go single and less parts to get hung up on the trails. You have plenty of room underneath to run it, so I would just run single. Just make sure you go 3". 2.5" would just put a hurting on ya.
 

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negative creep
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don't even bother with duals. you need way more than a stock engine to justify true duals. single 3" is perfect, i am running 40 series delta 3". check out the videos on my superford to see what it sounds like.
 

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Discussion Starter #4
Andy351 said:
don't even bother with duals. you need way more than a stock engine to justify true duals. single 3" is perfect, i am running 40 series delta 3". check out the videos on my superford to see what it sounds like.
First of all educate me, whats a delta 3? So is your exhaust basically a single inlet dual outlet? What about your cat/s? Are they factory or are they high flow aftermarket cat/s?
 

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Quote:
Originally Posted by Andy351
don't even bother with duals. you need way more than a stock engine to justify true duals. single 3" is perfect, i am running 40 series delta 3". check out the videos on my superford to see what it sounds like.

First of all educate me, whats a delta 3? So is your exhaust basically a single inlet dual outlet? What about your cat/s? Are they factory or are they high flow aftermarket cat/s?
no andy's is a single outlet, what he was saying was that there isnt enough power gains to justify having a true dual system (true dual system = drivers side headers running straight to a muffler and on the passengers side, headers running straight to a muffler via a seperate pipe.) also im sure andy would agree that having a single inlet dual outlet system is just pointless unless your doing it for cosmetic reasons only. About the sound of andys system, well I love it it sounds really good eventually I will probably be doing a similar if not same system. hope this helps clear up some stuff :thumbup
 

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Discussion Starter #6
So is the muffler the only difference between Andy's exhaust and a factory single exhaust? Another thing is I like the sound of duals, when using two 40 series mufflers with duals as apposed to one on a single exhaust it makes more of crackle sound which I like. And besides Andy could't have true duals if he wanted to because he lives in California where they make your vehicle go through those stupid emission tests.
 

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Charlie don't surf..
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I have to agree with Andy. I had the duals on my rig and removed them in favor of a single outlet exiting behind the passenger rear wheel. Less to get hung up on the trail and cheap to replace or fix. I have a single magnaflow stainess running through 2.5 inch pipe no cats, I'm really happy with the way it sounds and I think it runs even better then when I had the dual setup. Just my .02 cents.
 

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I have a flow 40 w/either a 2.25 or a 2.5 pipe...sounds and runs great

Bill
 

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Practicing Infidel
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I have a flow 40 w/either a 2.25 or a 2.5 pipe...sounds and runs great

Bill
Hey Metalhead

The jury is in and duals are out... on Broncos. If you've got the money to waste, the ground clearance to lose and a super talented pipe bender, knock yourself out, but I, like most everyone else went with an oversized single.

You asked about what cats etc. Here's what I created with a lot of help from a lot of the guys from the BBS forum (many of us are here too) particularly WD-40, whose design I more or less copied.

I priced a new Y-pipe with dual cats and it floored me, nearly $800.00 Canadian !!!!!! So I built my own with the help of a buddy who has a pipe bender.

I paid him to bend up full 2 1/4" head pipes for the Y-pipe that took me into a super affordable Y connector from Flowmaster. Both 2 1/4" pipes go into it and it comes out as a 3" pipe. I welded header flanges on the 3" pipe end and both sides of the Catco 3" high flow cat, which incidently you can read a paper looking through it (low restriction).

The new cat is not only higher capacity, but is a three stage eliminating the need for two stock cats and saving some real dough as it was @ $50.00 American from Summit. The new headpipes are not only larger than the stockers, but they have no kinks or that dreaded S bend over the crossmember as the new flowmaster Y and 3" pipe travels over it (gaining nearly 4" of ground clearance). There is a severe kink in the stock Y-pipe just off the passenger side manifold and it sure as hell ain't 2 1/4" I can assure you.

I did that much last year and built a header flanged reducer I could bolt on that necked me down to 2 1/4" so I could re-use my stock style 2 1/4" muffler and tailpipe last year as I was spent out.

I've just finished the last half of the sytem and it was not only pie, it was cheap. I welded up another $3.00 header flange to take me from 3" to 2 1/2" and went shopping for a mandrel bent tailpipe and larger 2 1/2" barrel shaped muffler because I wanted it to look semi-stock.

Bless Walker's hearts as they make the components of their Dynomax cat back system available seperately. I bought their full 2 1/2" mandrel bent tailpipe for the equivalent of $31.00 American. It is flawless, without any kinks, fits perfectly and dirt cheap(bless em' again). It also allowed me to buy anyone's 2 1/2" muffler and stick it together myself and cheaply.

The only drawback (in my opinion) was the squashed oval end tip that resembles a Jeep Grand Cherokee's. I sliced off the last 18" and necked from 2 1/2" up to 3" all the way out, welding it on. You could clamp whoever's tip you wanted on, even robbing a Honda if you so desired 5".

Like I said I wanted a round muffler and the Walker catalog didn't let me down. I measured up what would fit and bought the round 7" (or maybe 6 1/2" can't remember) universal 2 1/2" in and outlet with the exact factory offsets. Welded construction, available anywhere and $41.00 American, I got it even cheaper for $60.00 Canadian.

The muffler rumbles like a much larger V-8 and nobody believes me that it's a 302. That said it ain't loud enough to draw any unwanted law enforcement attention.

Power increases you ask ? The cat back advertising is bogus, false and just advertising. Like I said, I enlarged the cat forward part of the system last year much improving it's flow capacity. For the first time ever, even through a smaller stock muffler and tailpipe it barked the tires going into second and mileage was up noticably. This year with the catback system (albeit my own engineering) no vast improvement.

Conclusion ? You want flow ? Blow the first two dams (low flow stock cats and Y-pipe) before you blow the last third dam (the muffler and tailpipe). The muffler companies do what's easiest and cheapest for them and have to promise the feds not to screw with the cats. Now that you know the truth about cat back systems, work forward first.

Sixlitre

p.s./
BTW That $800.00 Y-pipe is still sitting at the parts store. We figured with the $38.00 Flowmaster Y fitting, $50.00 Catco 3" cat, Four $3.00 J.C.Whitney header flanges and the few hours labour charge, we saved over half doing it ourselves and built a much, much better mouse trap.
 

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Andy351 said:
don't even bother with duals. you need way more than a stock engine to justify true duals. single 3" is perfect, i am running 40 series delta 3". check out the videos on my superford to see what it sounds like.
You can't really say that either, because according to many charts single 3" is also overkill
 

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rem_243 said:
You can't really say that either, because according to many charts single 3" is also overkill
That's true except I'm 2 1/4" headpipes, 3" there through the cat, getting me the extra "potential" flow capacity. Attached to the 3" cat via a removable header flange (you can change it as often as you want and experiment) is a neckdown adaptor, first to 2 1/4" (last year) and now to 2 1/2" this year.

After the cat I've got it necking down to a 2 1/2" muffler and 2 1/2" mandrel bent tailpipe as opposed to the more restrictive 2 1/4" stock muffler and 2 1/4" kinked stock tailpipe.

I don't credit the last 18" of 3" tailpipe I welded on with any flow improvements, it's just there for my ego amongst other bigger trucks.

A lot of the guys at the other forum said exactly what you're cautioning me about the 3 " being overkill for the 302 and I was indeed worried about that.

That fact and the fact I was flat outta cash after the first stage "cat forward" system made me bolt back on the stock style 2 1/4" muffler and tailpipe last year to cork or limit flow and maintain enough back pressure.

I drove it 8 months like that and decided to step up to the 2 1/2" cat back system I bought(when money permitted). I doubt my vanity will ever make me step right up to 3" all the way back from the 3" cat, I'll probably stick with the 2 1/2" . Good point.

Sixlitre

p.s./
I take it you don't agree with a larger single or duals, is that right ?
 

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Sixlitre said:
p.s./
I take it you don't agree with a larger single or duals, is that right ?
No, i have dual 2.25"
 

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None2Slow said:
Not if its sized right. I have a 3" single setup on my 91 and its pretty nice. I know that the single has better scavenging to help pull the exhaust out of the ports, is cheaper to go single and less parts to get hung up on the trails. You have plenty of room underneath to run it, so I would just run single. Just make sure you go 3". 2.5" would just put a hurting on ya.
Look at the flow ratings posted....3" is ok with a 351, but a 2.5" ID pipe will do just as well. You got 300+ HP? if not and if you aren't going to remove any neckdowns right after the cats, then a single pipe 2.5" is ideal.
 

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Are those REAL?!?!
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Exhaust is a toucht area where an engine is concerned, if it breathes too much, it affects low end torque, if it doesn't breathe enough, it affects actual horsepower, and the power band of the engine. The best thing I learned when I began tinkering with cars way back when on my '67 Cougar, was that an engine, in it's most basic description, is simply an "air pump". Yes, this is far from a detailed description, but the concepts and principles are the same...

Match the output with the input, and you'll be just fine, and make efficient power (hp+tq).

Catco makes a great, inexpensive catalytic converter that flows well. Available from Summit. The rest is all personal taste. Flowmaster, Flowtech, Dynamax, Hooker, etc... all make good flowing mufflers...

Flowtech headers aren't the best choice, but their mufflers rule!! I like the "Terminator" line personally.
 
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