3" exhaust system for a mild 383??

[cougs]

Hi all,
I'm looking at the TTI exhaust systems.  Is there a problem by going with a 3" system rather than a 2.5" system on a mild 383?  Will I be hurting performance or will it sound strange?  I like the look of 3" pipes coming out the back and want to be ready for when I go to a stroker someday.   I plan on going with 1 7/8" headers.  Any issues with this.  Obviously I won't see a power increase. 

[Cooter]

I don't think so, it prolly won't be long before you install a stroker. 3" never 'hurts"....

[cougs]

That's what I'm thinking.  I've heard of problems with going too big on header primaries but not the pipes.  Plus this will motivate me to get the stroker kit. 

[charge69]

I'm sure you can use either the 2 1/2" or 3" system. If you like the looks of the 3" system, get it.  Just be advised that it will give you a little less clearance from the road. Probably not enough to worry about, though.

I will tell you that my supplier (a VERY well-known MOPER gentleman) told me a 2 1/2" system is all I really needed on my HEMI so, I bought a complete 2 1/2" X-Pipe exhaust system for my HEMI that has 2 1/8" tube headers (also recommended for my engine) and I am completely satisfied with the look, performance and sound of the system! It sounds and looks completely BADAZZ!

[Chargen69]

i went with headman elite headers on mine. 1 3/4 primaries, 3"collectors and 3" stainless steel pipe into 3"mufflers with turn downs for now.  i have had 2 1/2" pipes on a different 69 with a 383.  Havent been down the road with mine yet, but already i like the sound better and the throttle response is a little better than my old charger, so i am happy with it.

also, we did put a TON of sound deadner in the car, so I hope most of the drone at speed will be okay

[A383Wing]

engines need a certain amount of back pressure to make HP....sometimes a larger exhaust system will actually hurt performance

bigger ain't always better...just as in carburation

[BigBlockSam]

go with a 2.5 inch . 3 is to big  for a mild 383 . not enough back pressure 

[Kern Dog]

NOT enough back pressure!

[cougs]

I don't understand this back pressure thing.  I thought open exhaust and headers was the ultimate!?

[Ghoste]

Yes to a point.  With the way an engine operates though it is subject to wave principles.  This is all very much oversimplyfing but basically the necessary amount of backpressure ensures that energy is available to contribute to the next wave of pressure and give it strength.  I don't know the correct way to phrase it but an engine cylinder creates power in a sine wave and back pressure to a degree keeps that wave from flattening out.
Someone else will explain this better but no back pressure would result in a lower overall power output.

[c00nhunterjoe]

Wait, so you need backpressure, but flowmasters are bad because they cause backpressure and you need a straight through muffler because they dont have backpressure... oh ok, got it...  

On a mild 383 2.5 would be good in 90% of the cases. What is done to it? What trans and gears do you run? I can tell you that my mild 383 loves the 3" exhaust i am running. I too like the sound and tone it has over the equivalent 2.5" systems.

[c00nhunterjoe]

Yes to a point.  With the way an engine operates though it is subject to wave principles.  This is all very much oversimplyfing but basically the necessary amount of backpressure ensures that energy is available to contribute to the next wave of pressure and give it strength.  I don't know the correct way to phrase it but an engine cylinder creates power in a sine wave and back pressure to a degree keeps that wave from flattening out.
Someone else will explain this better but no back pressure would result in a lower overall power output.

Right, this is where the h pipes add horsepower and x pipes even more. It uses the engine pulses to scavenge the air and essentially create a vaccum in the opposing open exhaust valved cylinders aiding in lost hp prevention.  Another reason the nhra stock and superstock cars run on average, 18" collector extensions.

[green69rt]

Just going to throw   in here because, from what I've read on this forum Cooter and Ghoste seem to have good info.   And from what they say "it all depends".   If I may interpret, bigger pipes allow more horsepower (at the top end and even throughout the power band ) but it MAY be a trade off on low end torque.  If the engine is built to take advantage of the bigger pipes then things are good , if not the owner may be disappointed.  So... do some planning and figure out the end result desired before spending bucks for no need.

I think I've read several threads on this same subject and it's always interesting and informative.  Same with H pipes, X pipes and just plain exhaust.

[RallyeMike]

The header primary size is much more important.  After that, the pipe size in this case won't make much difference either way.

[c00nhunterjoe]

Fwiw, i run 516 heads with 1 3/4 tubes into 3" exhaust. For my particular combination it works out great. My car doesnt really "come alive" until midrange and screams on topend

Let me clarify: its not a dog down low but if i floor it from an idle it doesnt roast the tires. It picks up the front end and starts to pull. As it hits 2800 its like a switch gets turned on and it literally explodes to life. Thats how my combo is setup. She idles at 1300, skips off the cam till every bit of 2000 rpm, but dont let that fool you. Its a blast to cruise, race or even take on the highway (limited to about 65-70). I have no issues with low end horsepower or torque when it comes to driving around town. If i want i can lug it down to nearly idle speeds but it will skip off the cam and eventually lurch the car as it skips(4 speed) if i do it too long.
    The point im trying to make is plan your whole vehicle combination, not just an engine or trans or tires seperatly. You will be much happier with how the car performs.

[cougs]

This is what I understand.  Headers with too large of primaries can make an engine a dog but after the headers it really doesn't make a difference and the less backpressure the better.  I just don't want to make sure it won't sound weird.

 

The header primary size is much more important.  After that, the pipe size in this case won't make much difference either way.

[c00nhunterjoe]

This is what I understand.  Headers with too large of primaries can make an engine a dog but after the headers it really doesn't make a difference and the less backpressure the better.  I just don't want to make sure it won't sound weird.

 

The header primary size is much more important.  After that, the pipe size in this case won't make much difference either way.

Honestly, to nit pick, i would say run a step header starting with whatever size matches your port. So for example, in my case, the 1 3/4 stepped to 1 7/8 up to 2" into the 3" collectors. But thats extremely picky and unpracticle unless you are lookingnto squeezenevery ounce of power

[Cooter]

Um, he did say he was doing a big inch stroker later on. Big motors need to breathe. To hell with the 383 that's in there now. It can't hurt a 300 hp engine that much. If a 3" exhaust with headers, hurts performance, then someone please explain why one can drop the pipes at the track and almost always makes more power with open headers?

[BigBlockSam]

Yes to a point.  With the way an engine operates though it is subject to wave principles.  This is all very much oversimplyfing but basically the necessary amount of backpressure ensures that energy is available to contribute to the next wave of pressure and give it strength.  I don't know the correct way to phrase it but an engine cylinder creates power in a sine wave and back pressure to a degree keeps that wave from flattening out.
Someone else will explain this better but no back pressure would result in a lower overall power output.

good stuff Ghoste 

[RallyeMike]

I just don't want to make sure it won't sound weird.

It won't sound any weirder than whatever 2-1/2" system you have planned, just louder.

[cougs]

I just don't want to make sure it won't sound weird.

It won't sound any weirder than whatever 2-1/2" system you have planned, just louder.

Well louder is good!  I've hears 3" pipes on a couple mild chubby 396s and it sounded pretty mean.