2” or 2 1/2”

Mopar Exhaust Systems

  1. Red63440

    Red63440 FBBO Gold Member FBBO Gold Member

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    My 64 Fury was upgraded to a 383 this past summer. Before I could finish the exhaust I ran out of warm weather. The dual exhaust that came with the car is just about new with Flow Masters, all nice and shiny. The car isn’t going to be raced and will just be used for cruising. Exhaust pipes measure just a little over 2” OD so I am guessing they are 2” ID. Question is, is it worth upgrading to 2 1/2” pipes for a cruiser from new 2” pipes off of HP manifolds.
     
    Last edited: Nov 23, 2021
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    • bearman

      bearman FBBO Gold Member FBBO Gold Member

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      I would run what you got. Until the sun comes out again then decide if you want to move up to 3 inch.
       
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      • Red63440

        Red63440 FBBO Gold Member FBBO Gold Member

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        The car is in the garage for the winter, I didn’t get the chance to get the new head pipes made from the HP exhaust manifolds to the existing system.
         
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        • 33 IMP

          33 IMP FBBO Gold Member FBBO Gold Member

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          For a cruiser, with manifolds, I wouldn't bother replacing a new system . With headers, I would use a 2 1/2 minimum, but I like 3"

          But headers kinda move it out of "cruiser" status.
           
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          • 69 Sleeper Bee

            69 Sleeper Bee Well-Known Member

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            I would stay with the 2'' if they are new. Like you said it is a cruiser not a race car.
             
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            • Ron H

              Ron H FBBO Gold Member FBBO Gold Member

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              I got talked into 3” exhaust on my pepped up poly rebuild with TTI headers and X. A mistake. Longer story as I did some researching should have done sooner. Oversize exhaust robs HP. 3” is generally for motors exceeding 450 HP. I’m around 100 shy. Installed hemi mufflers replacing the 50 series flow masters (too loud for me) that, go figure, have a max of 2.5”. My quick guess is you’d want 2.250 maybe 2.50 max for your setup if you want to go through a changeup. But, this depends on what the costs of a change over means to you as opposed to leaving it be since you have a nice system. Maybe 10 HP…my guess...
               
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              • WileERobby

                WileERobby Well-Known Member

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                No. period.
                 
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                • 66Satellite47

                  66Satellite47 FBBO Gold Member FBBO Gold Member

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                  OP, are you just asking about the pipe from HP manifold to muffler? With 2" back from the muffler?
                  I'd sure consider 2 1/2 from manifold to muffler, but if the 2" will fit the HP manifolds, try it. If you are satisfied, leave it.
                   
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                  • Big Bad Dad

                    Big Bad Dad FBBO Gold Member FBBO Gold Member

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                    I installed a TTI 2-1/2" dual exhaust kit on my 64 Fury after changing over to the HP style manifolds. I like it a lot, and it fit well. But I was also replacing the original skinny pipe single exhaust on my 361. You need to provide TTI with the casting numbers from the manifolds so they can make the head pipes with the flanges oriented in the right direction. DSC00867.JPG
                     
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                    • rumblefish360

                      rumblefish360 Well-Known Member

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                      Sorry bearman & 33 IMP, but why 3 inch pipe for a cruiser? Pipe size should be sized for the amount of power the engine has. I do not see a HP level attached to this post. If it is elsewhere, it should have been included here. And why do headers magically move it out of cruiser status?
                       
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                      • CMCE

                        CMCE Member

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                        If you are satisfied with the way your car sounds, just leave it. At your power level and intended purpose, you will gain little to nothing with a bigger exhaust. A 2" dual system will support around 300hp. Even if your engine dyno's at more than that, you're not using that HP just cruising around, and the smaller diameter pipe keeps exhaust gas velocity up which helps with low end torque. Now if you're making a lot more power than that and you're racing, everything I stated above goes out the window....
                        Beautiful Fury BTW!

                        https://www.classicmusclecarexhaust.com/exhaust-101
                         
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                        • rumblefish360

                          rumblefish360 Well-Known Member

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                          @Red63440 These guys below.
                          :thumbsup:
                           
                        • Red63440

                          Red63440 FBBO Gold Member FBBO Gold Member

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                          The engine is a 1970 383 HP block with factory flat tops, compression is 9.4/9.5 through 516 heads with oversized stainless steel valves and 0.20 shim steel head gaskets. Intake is a Edelbrock Performer with a Edelbrock 650 CFM carb, electronic ignition, voltage regulator and Engel cam just slightly hotter than what came in the road runners. As stated I am running HP manifolds through dual 2” exhaust with Flow masters. Thansmission is the original 3 speed automatic with valve body and push button shift. Gearing was just updated to 3.23 sure grip in a 68/70 8 3/4” rear end housing. I haven’t had a chance to drive the car since all the changes but I am hoping for the best. Thanks for the input!
                          EC3C7C5A-B2F1-4FFC-9F27-E2D46D703C7B.jpeg 500E3CE6-7107-49AD-AFE3-E7F940073917.jpeg CFFDA904-4EC1-40DE-9787-2EFF52C9355A.jpeg
                           
                          Last edited: Nov 24, 2021
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                          • toolmanmike

                            toolmanmike Henchman #2 Staff Member FBBO Gold Member

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                            2" is fine. If you replace it, go with 2 1/2". 3" is a waste for your combination and use.
                             
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                            • Don Frelier

                              Don Frelier FBBO Gold Member FBBO Gold Member

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                              I would suggest driving it a bit.
                              Then if anything maybe convert what you have to an H-Pipe.
                              It will sound different from behind if you do that.

                              But no I really don't think you would gain much by upsizing the pipes.
                              Your cam isn't going to pull hard much past 5,000 rpm anyway.
                              We had a 66 Newport 383 with single 2-1/4" exhaust that was a highway killer with log manifolds and two barrell carb.
                               
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                              • 33 IMP

                                33 IMP FBBO Gold Member FBBO Gold Member

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                                To me, a cruiser doesn't need headers. If it has headers on the car when it is bought, that's different. If the owner is installing headers, that means he is after a certain level of performance, such that he is willing to put up with the downsides of having headers. In that case, like I said, I would use a minimum of 2 1/2.
                                I have three cars with headers, none of which are remotely cruisers. All have 500+ fwhp, one has 3" exhaust, the other two have 3 1/2.
                                Edit: if you re-read my post, you will see I advised the op against changing his new 2" system.
                                 
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                                • rumblefish360

                                  rumblefish360 Well-Known Member

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                                  I agree a cruiser doesn’t need headers, but to say a certain performance level is sought is a very wide & open to interpretation. My 5.9 Magnum in a ‘79 Magnum cruiser has 1-3/4 headers, 2-1/2 exhaust, aluminum intake w/a 4bbl & a recurved distributor.
                                  IMO, all I did was maximize what I have with bolt on parts. No cam change, no shift kit. Back by a 727 & 3.55’s. It is a drive anywhere at anytime vehicle.
                                   
                                • 66Satellite47

                                  66Satellite47 FBBO Gold Member FBBO Gold Member

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                                  Agreed, headers are not needed for a driver car, but can be helpful. My '70 Barracuda 383 liked the change to headers & a 4 bbl. Ran better, better MPG if I kept my foot off the floor. My '76 Doge van daily driver/tow vehicle really liked the swap from 318 to 360 with headers, much better for towing and at least 2 mpg better mileage all the time.
                                  But for the OP, try what he has and change if he wants to. There is some power and mpg in a good coordinated exhaust.
                                   
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                                  • barbee6043

                                    barbee6043 Well-Known Member

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                                    ^^Like aid, leave it.
                                     
                                  • bearman

                                    bearman FBBO Gold Member FBBO Gold Member

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                                    I think as i said before drive until he needs three inch. After the sun comes back out and he drives it he may want to up to a little more power. You and i both know its hard to leave a mopar alone. So for now i agree leave it alone.
                                     
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