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what size exhaust to run?

3767 Views 19 Replies 11 Participants Last post by  santak, 
H
73 ..p/w 360 ...no headers . wanted most torqe..dual.
...my pipes need to be replaced soon they are rusted and small .....what size is everyone using? ..and what about mufflers ? i dont want to spend 100 dollars on one muffler . so flow masters are out of question :)
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loosewheelbob
I think that alot of people are using 2 1/4" pipe these days, if you go too big, you could lose some low end torque. As far as Flowmasters being out of the question, you can get the 40 series for around $60 in summit. I got my 40 series for $40 at a local shop, and it sounds great, a nice rumble at idle and highway speed, but when I floor it, it doesn't get obnoxiously loud like glass packs do.
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mopar65pa
I have a 2 1/4 system and a 2 1/2 system the smaller one has headers and the bigger one dosen't. The 2 1/2 sounds awesome with cheep turbos on it ( it's a 360 ) the 2 1/4 sounds pretty good too with the same mufflers on it but dosen't have the same deep rumble ( 318 headers )
I like the sound of a 2 1/2 better. My .02$
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R
Ive got 2 1/4 on mine with cheap turbo glasspack looking things with baffles and no glass, sounds just like a flowmaster, my exhaust guy must have been retarded or somthing, he told me he couldnt put real flowmasters on it cause there is not room and they weigh too much its a 76 Powerwagon, and you guys are telling me you have them on there? :mad: GRRR that makes me mad, lol. Its duals that run down the passenger side and turndown right before the axle.

Eric
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mopar65pa
there should be plenty of room cause the duels on a truck have to run on the outside of the frame due to the gas tank. :-\
The little reds came from the factory with duels and turbo type mufflers.
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E
Go with a single for low end
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M
You can install the Flowmasters on edge on the passenger side inside the frame next to each other. I don't know if it's appropriate to mention it here, but I have a pair uf used flowmasters available for $30 each plus shipping
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S
Yeah, what Marty said. If you want torque, dump the dual exhaust. If you want to run headers in the future you can run 2 1/2" into a single 3". With the stock exhaust manifold stepping up to 2 1/4 back to the Y, then 2 3/4" or 3" would be about it.
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H
Uh..I agree whole hartedly with the single exhaust part, but people c'mon, have we all forgotten about tuning our exhaust here? The formula is simple and is as easy as plugging in a couple numbers and wella...tells you the distance away from the port to put your muffler inlet. I can tell you from experience and from the advice of a gentleman named John Force, that tuned exhaust makes a "noticible difference"to your acceleration and torque. I urge anyone who is doing an exhaust replacement anyway, why not tune it! Costs the same in most cases.
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loosewheelbob
Hemi2003 said:
The formula is simple and is as easy as plugging in a couple numbers and wella...tells you the distance away from the port to put your muffler inlet.
Click to expand...
Can you share this formula with us uneducated folks? How do you determine the numbers to plug in? You got my curiosity, and I'd like to know for future reference.
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H
ok look here http://victorylibrary.com/mopar/header-tech-c.htm
..what rpm is max torq on a stock 360?
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E
Lmao tune your exhaust, let me know when your up to about 2 grand how it's coming out, 1st to tune your exhaust you need to start at the head and work your way back and it includes making headers with a particular size primary and what tubes run into the collector and how, this is not simple, this is not cheap, this is not fast, but if you got the time and money do it, start with making a dyno date.
This is very involved
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oldmanram
Ok - Just so I'm on the right page here.
If I want a little more low in torque out of my 318, I build a new 'y' pipe set-up out of 2-1/4" pipe from the stock manifolds, back to the cat (I'm using a Summit full flow cat). Then 2-1/2" from there. I've got it cut off and down turned just before the rear axle (does overall length make any difference). Right now I just have a cheepie glass pack, but thats just 'cause I wanted to get rid of the stock muff. :)
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M
A few of you have said that a single system will make more torque. Why does it? Can anyone explain this or point to some test results that prove this theory?
Thanks in advance.
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oldmanram
Moparman440 said:
A few of you have said that a single system will make more torque. Why does it? Can anyone explain this or point to some test results that prove this theory?
Thanks in advance.
Click to expand...
Yes - Good question - I've heard this before, but never questioned why....
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H
so what i assume is a single for torque. or according to the link i posted one and a half inch dual ..thats what i have now . i just dont know .... but i feel that this is important for a proper towing set up. thanks all
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G
Actually single or dual exhaust can be built for power or torque. If you want to figure out what size a single exhaust pipe would need to be to flow the same as a dual exhaust you need to figure out the cross area of the pipes in question. The formula for this (circle area) is Pi(3.1416) x R(Radius of Circle or Pipe) Squared. For example the cross areas (section area) for 2" = 3.14 sq", 2.25" = 3.97 sq", 2.5" = 4.91 sq", 3" = 7.06 sq". As you can see a single 3" exhaust system flows more than a dual 2" system and 89% as much as a dual 2.25" system. The benifits of single exhaust are: Less weight, Less expense, No need for balance tube or cross-over pipe. Additionally the tube from the Y-pipe to the Cat or Muffler acts like a collector and builds torque. If you have stock manifolds you will probably have to go with 2" or 2.25" to the Y-pipe (mounting socket diameter on manifold is limiting factor). If you have headers the pipes to the Y should be the diameter of the collector (2.5" for all the 318 RC headers I've seen) then to 3". Summit has 318RC headers for $80. The set-up I'm getting ready to install on my '86RC 318 is a set of Thorley Tri-Y's (1.625" primary, 2.5" collector) to 2.5" sectioned and welded mandrel bends to a flowmaster Y-pipe to a Dynomax 3" Convertor to a Dynomax 3" Ultra-Flow round muffler dumping out behind the axle. This is a little pricey (@700 in parts + labor if you can't fab yourself) but you could do it on the cheap for @180 (summit headers 80, Catco Cat 60, cheap muffler 40) + muffler shop bending up some custom steel pasta. Single exhaust doesn't have the muscle appeal of true duals, but make power if designed correctly (ie. latest Camaro SS runs single exhaust 325?HP)
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E
Actually a built single exhaust with a merge pipe will sound just as good as a dual without the raspy crackle, but still have the muscle appeal
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oldmanram
Evildriver-3 said:
Actually a built single exhaust with a merge pipe will sound just as good as a dual without the raspy crackle, but still have the muscle appeal
Click to expand...
I know you make these posts just to make a crazy person more CRAZY --- be specific..... :D
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S
Well, to add to this discussion if it helps any:
I just put a 3" single exhaust on mine and picked up 2 mpg at the last fill up tonight. I had everything done from the manifolds down. Don't have the exact number for the pipe into the cat, but I would guess it some 2.25"-2.5" and then out back the bigger 3". Mandrel bend. Cost was 500 plus tax.
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