2" to 3" exhaust... Worth it?

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Sdriche

Sdriche

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Wondering what preformance gains I could expect going to a bigger exhaust. Currently have a 360, 4bbl, with headers going to a 3" collector. The rest of the exhaust is 2"all the way back..true duals. 323 suregrip rear. Would a3 inch or 2.5 do much or leave as is? Thanks
 
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It's not so much the size as the type of bending. Mandrel bent tubing will have significant performance gains. Since it's quite rare to see 2" mandrel bent exhaust, you will be looking at 2.5" for your application.

An very common example of a 2" crimp (oem style) bent system swapped out to a 2.5" mandrel bent system on a car with 400hp, you'll get easily 35 hp. It's more normal to get 50hp!

Some may not believe it but we did extensive dyno testing for several years on all our Pypes systems and kept getting the same results time after time. Mandrel bent exhaust is like night and day performance wise.
 
Sdriche said:
Wondering what preforms gains I could expect going to a bigger exhaust. Currently have a 360, 4bbl, with headers going to a 3" collector. The rest of the exhaust is 2"all the way back..true duals. Would a3 inch or 2.5 do much or leave as is? Thanks
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It’s build dependent.

As for what I do, 2-1/2 on a street bound, true driver, stock 360 or up to 450 HP if a turbo or chambered muffler is used. In this power range, as Moparoffical said, this is still small cam territory.

A 3 inch dual exhaust I’ll use for a more powerful set up which would include a larger cam. For the street, for me, this is IMO as opinions vary from person to person, a big street cam is a Hyd. 248* @ .050 or a solid @ 255 @ .050. If you fully take advantage of what the cam has to offer, I believe a 3 inch dual exhaust would be right.

Between the styles of doing a dual exhaust, true duals is fine. A few foot pounds of torque and HP can be found by adding an “H” pipe. And then again but at a much smaller margin with an “X” pipe.

I do “H” pipes because there easy to install or even make on your own. The X pipe is not worth the hassle IMO or cost. But I did do one on the wife’s 360. The sound does change and the higher you go in rpm, the more it shrieks like an angry banshee coming for you with vengeance.
 
Good video that I’d like to make one notation, which would be the mufflers used are straight through styles. Not turbo or chambered.
 
rumblefish360 said:
Good video that I’d like to make one notation, which would be the mufflers used are straight through styles. Not turbo or chambered.
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Agree! There can be a big difference in cfm with a straight through muffler vs a chambered or turbo type muffler especially if you are racing the car and trying to get every single HP you can possibly get.

That being said, for everyone reading, the pipes have a much greater affect on the exhaust systems performance than the mufflers do regardless of what mufflers are chosen..... well I mean short of putting a cork in there! :lol:
 
Just going from 2 inch to 2.5 inch will increase the flow by two-thirds, and that's not even taking into consideration crimp bent vs. mandrel bent. Horsepower potential goes from less than 300 for a 2 inch dual exhaust to over 450 for 2.5 inch setup. Then there's a three inch system for the big boys.

upload_2021-12-28_17-25-50.png
 
Engine Master Season 6 Ep 83 they do a test between crunch bent tubing and mandrel bent tubing ,,,,,,with and with out mufflers....

how the tubing was bent made no difference on a 500 hp engine......and Dynomax Turbo Muffler made as much power as the straight thru muffler

you can get Motortrend for 3 dollars a month.....join now before the price goes up....LOL
 
Good post with the pipe size listings. Now the trick is get a muffler that will flow as well. The straight through is the only one no matter what deadens the sound within.

David Vizard wrote a flow rate of 2.2 cfm per HP is what is needed for a nonrestrictive exhaust which will allow maximum power.

If you can find the flow rate of the muffler you want to use, in which is ether based on power or sound, OK, maybe both even, but if sound is what your after, find the flow rates of the various size offerings.

It would be advantageous to use a muffler the next size up from the pipe you have and then continue the pipe size after the muffler. This can also help keep it quieter.


Brooks James said:
3 inch no nagging question about are my pipes big enough
Plus bragging rights
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The only pipe worth bragging about should be behind your pants zipper.
:thumbsup:
 
Sdriche said:
Wondering what preforms gains I could expect going to a bigger exhaust. Currently have a 360, 4bbl, with headers going to a 3" collector. The rest of the exhaust is 2"all the way back..true duals. Would a3 inch or 2.5 do much or leave as is? Thanks
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On the street or at the track?
For a streeter;
How often will you be at WOT with the tires Not spinning?
Lemmee guess, from 50 mph to 65 mph, in Second gear.
Lemmee guess with 3.23s and a torqueflite, this would be about 3350 rpm to 4360
I don't think the engine will care, and even if it does, I don't think you could ever measure it, in ET.
So I say;
leave it as it is.
 
65 Cuda 340 said:
When I was younger - A LOT!!!!
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With the way AJ puts things forth, it is as if you have no choice but to spin tires and the engine is to powerful for the road to drive safely which of course means your to stupid to know how to control your right foot. Also, should your car be powerful enough to spin tires at speed, be it at 35, 55 or 75 mph, you probably need better tires. OH wait a minute! You mean you designed your engine to be this powerful????? Nevermind. LOL!!!

Dont worry OP! In AJ’s mind, there’s only one way to build a street machine, his way and everyone else doesn’t know what there doing.
 
Right now, I can't find the tables and such I used to make my decision.
Once my 360 gets put in the car, it's getting Doug's D453 headers with 2 1/2" pipes and an H pipe. I made these decisions based on what I was able to learn about scavenging and a pack of unladen 'MURICAN swallows air-speed-velocity as they travel in line down the exhaust system and out the pipe. I chose my stuff based on MATH, not how cool it may sound.
Larger diameter pipes than what I have at the output of my small block build; cam, intake, heads, headers et cetera, would not provide as good scavenging and hence intake charge for the next suck-squeeze-bang-blow cycle.
 
rumblefish360 said:
With the way AJ puts things forth, it is as if you have no choice but to spin tires and the engine is to powerful for the road to drive safely which of course means your to stupid to know how to control your right foot. Also, should your car be powerful enough to spin tires at speed, be it at 35, 55 or 75 mph, you probably need better tires. OH wait a minute! You mean you designed your engine to be this powerful????? Nevermind. LOL!!!

Dont worry OP! In AJ’s mind, there’s only one way to build a street machine, his way and everyone else doesn’t know what there doing.
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Pretty much, 100%
 
@rumblefish360
Again;
you totally missed the point.
Here it is again; maybe read it a few times . Maybe you'll get it.
AJ/FormS said:
On the street or at the track?
For a streeter;
How often will you be at WOT with the tires Not spinning?
Lemmee guess, from 50 mph to 65 mph, in Second gear.
Lemmee guess with 3.23s and a torqueflite, this would be about 3350 rpm to 4360
I don't think the engine will care, and even if it does, I don't think you could ever measure it, in ET.
So I say;
leave it as it is.
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How fast can OP go in first gear? With a stock cam, the shift rpm will be about 5200 rpm. With 3.23s, and 27s this will be about 44mph. At the shift, the rpm will drop to ~3100,
I purposely said 50 to 65, because 50 is 3350 in Second, but maybe 5700 in First , so that allows a lil wiggle-room in the tires, gearing, or shift rpm. You know, in case I was wrong about the cam being stock, or the gears not being 3.23s, or the tires not being 27s. But it is a more than reasonable baseline to Not be spinning , which answers the first question.
OP gave us a detailed description of his combo, and it doesn't mention anything beyond bolt-ons, so I assumed the short was stock. I don't know any stock 360 shorts that are gonna spin the tires at 3350 rpm in Second gear, so I believe this is a valid scenario.
So then the question is, how much power can the stock 360 short with bolt-ons generate from 3350 to 4360, and does it warrant laying out the cash for a bigger exhaust?
Next; how often will OP be in this situation?, and does that warrant the expense of the bigger pipes?
As we all know, at less than WOT, the 2"pipes he now has is are adequate.
Will the 2" pipes hold his engine back in first gear? Not if the tires are spinning; the exhaust size is not a problem.
Will the 2" pipes hold his engine back at less than WOT in First gear. Not hardly.

And finally, Rumble, you are the guy who constantly rails on me to NOT spend an OP's hard earned cash,
yet here you are, once again railing on me, this time for trying to save an OP some significant amount of money..
 
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Not a lot of room for a 3 inch exhaust in an a body. Mine had a new 3 inch exhaust on it when I bought it. I didn’t like the look, fit or the sound. Took it off & sold it. Just an opinion…..
 
My apologies AJ, your post was short.
Assumes a bit as usual.
Below is a crop that gets to the point of where it’s at for the OP.
AJ/FormS said:
So then the question is, how much power can the stock 360 short with bolt-ons generate from 3350 to 4360, and does it warrant laying out the cash for a bigger exhaust?
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Answer, in the 270+ hp area.
Yes, that’s the question and your answer is a yes or no?

And finally, Rumble, you are the guy who constantly rails on me to NOT spend an OP's hard earned cash,
yet here you are, once again railing on me, this time for trying to save an OP some significant amount of money..
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Minor correction, while I do say help a guy save a buck, I also say help him other ways (looking for whatever, in this case power) that may or may not save him a buck.

IF it is your opinion that a 2-1/2 exhaust system is a waste of his money, then just say so.
 
Run 3" off the header collectors up to the mufflers then run 2.5" mufflers and tailpipes. Your engine won't make use of 3" exhaust but keeping it the same diameter as the header collectors will boost torque in the low-mid-range by extending the secondary header tuned length. I already have 2.5" exhaust on my Duster with a ~450 HP 360 but plan to put in the bigger pipes from headers to mufflers when I install my Doug's D453 longtubes.
 
The best way to get the most torque is with the same size exhaust pipe as the collector for a certain amount of inches, which varies. Engine masters did a thing in that. I don’t want to blanket statement “Use an 18” length of pipe…” At the pipes end, you need a pressure cancellation box or at least as many square inches as the engine is. Then continue with the exhaust pipe into the muffler.
 
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