TTI 2.5" or 3" exhaust system?

Mopar Exhaust Systems

  1. Justin Smith

    Justin Smith Well-Known Member

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    I know this seems to be a common thread, However I hadn't found the answer I am looking for yet. I have a 426 Hemi with TTI headers, a A833 4 speed, Dana 60 rear end, Hotchkis shocks. I am Looking to purchase an exhaust system from TTI. I would like to purchase a 3" X pipe exhaust, however, has anyone had any issues with installation of a 3 inch system on a 1970 Super Bee? Does the 3" have clearance issues? I'd just assume get a 2.5" exhaust if it has a better installation. what do y'all think?

    Thank you,
    Justin
     
  2. 451Mopar

    451Mopar Well-Known Member

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    I have the 3" "H" pipe crossover version on the '71 Charger and it fits good. No issues with it.
    I have the 2.5" "X" pipe on my '69 Coronet Convertible. Main reason I went 2.5" was to use a non-performance "quiet" muffler.
    Not like I'm going to be racing the Convertible at the track that often.
     
  3. Darter6

    Darter6 FBBO Gold Member FBBO Gold Member

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    I've never used anything larger than 2 1/2'' .
    I can only say the folks that have installed 3'',"most" state that they wish they didn't.
    Most deal with clearance issues from what I have heard.No real gain in HP performance.
    It may have to do with body type/style.
     
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    • Justin Smith

      Justin Smith Well-Known Member

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      Did they not like the noise level after they had it installed with 3"?
       
    • hunt2elk

      hunt2elk FBBO Gold Member FBBO Gold Member

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      TTI talked me into going 3" on my 69 Bee because of the 600 hp motor. Sure wish I would have did 2.5 instead. 3 inch is a lot louder and very tight by the gas tank.
       
      Last edited: May 31, 2020
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      • Justin Smith

        Justin Smith Well-Known Member

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        The Hemi in my car was apparently one of the Indy Cylinder head 426 street engines. they say it dyno'd 535HP 500Ft Lbs of torque. I like loud cars but I reckon that's cause I am young. Exhaust close to the gas tank sounds kind of scary to me, I'll probably just get the 2.5" exhaust system.
         
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        • steve340

          steve340 Well-Known Member

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          Magnaflow publish their recommendation for exhaust pipe size based on the power output of the engine. The is a lot of info on this subject on the internet.
          My personal opinion is street cars with engines under 450 cubes and not highly tuned do seem OK with a quality 2.5 inch mandrel bent system.
           
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          • 493 Mike

            493 Mike FBBO Gold Member FBBO Gold Member

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            There are plenty of insulation materials now available to cover those close "encounters".
            Mike
             
          • zyzzyx

            zyzzyx FBBO Gold Member FBBO Gold Member

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            A Hemi moves some air. Flow numbers are not what us wedge boys are used to!
            Look at the charts and think about what you're going to do with the car and then make a decision.
             
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            • Darter6

              Darter6 FBBO Gold Member FBBO Gold Member

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              Justin, Not the noise, but I guess the tight fit (one guy did a 67 small block Dart, another a 67 Coronet R/T 440) mostly with the cross member area and tail pipes. Again I'm sure it depends on the year and body style.
              I too have heard the 600+ HP figure for the larger exhaust. Just puttin' it out there.No disrespect.
              You are pretty new to the site, Your gonna hear "It's your car do what you want" when it comes to many decisions when questions are asked.
               
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              • Justin Smith

                Justin Smith Well-Known Member

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                I'ma roll with a 2.5" exhaust, it'll do the job I need it to do! It'll perform just fine I believe. If i want to make some noise, I have a 1970 Dodge Challenger tube chassis drag car with a 557CI that I can make noise with! hahaha! I have had the Challenger since I was 19 years old. thanks for all y'alls responses!
                 
              • diesel_lv

                diesel_lv Well-Known Member

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                I've got a '67 Coronet stroke 496 w TTI headers n 3" H pipe exhaust. I'm right at 600 hp. Super tight at gas tank. Rubber mallet work to the gas tank flanges. Took 5 hrs by myself w car over 1-1/2 feet up on Jack stands. Total PITA!!
                 
              • hunt2elk

                hunt2elk FBBO Gold Member FBBO Gold Member

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                I have heard of guys running 3 inch through the mufflers and then going to 2.5" tailpipes. This is the route I was going to try. Mike at TTI said he would make it for me, but doesn't recommend it. He thinks it negates the purpose of 3 inch.
                 
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                • 493 Mike

                  493 Mike FBBO Gold Member FBBO Gold Member

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                  Lots if not most stock exhaust systems use a smaller diameter tailpipe. The thinking here is the exhaust is cooled in the muffler so there is less volume and the smaller size helps keep the velocity up through the system. It also costs less for the manufacturer (bean counters love some engineering)!
                  Mike
                   
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                  • snakeoil24

                    snakeoil24 FBBO Gold Member FBBO Gold Member

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                    Save yourself a lot of money buy a 2.5 Pypes stainless exhaust with the tti headers. Why spend all that money for tti exhaust and its only aluminized.
                     
                  • Joske2

                    Joske2 FBBO Gold Member FBBO Gold Member

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                    3" system on my '70 Coronet, no clearing issues. System is TTI . SAM_6495.JPG SAM_6496.JPG SAM_6497.JPG

                    The only modification we had to do is cut just before the H-pipe, to bend the pipes upward so they are close against the floor. After the muffler we welded V-band camps, so we could get the right angle to go over the rear axle. The muffler hangers are only there to support the system.
                    All was TIG welded. We did a lot of measuring and test fitting before welding, and it took about 8 hrs with 2 on the lift.

                    Will see if i have more detailed pictures.
                     
                    Last edited: Jun 1, 2020
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                    • 69 GTX

                      69 GTX FBBO Gold Member FBBO Gold Member

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                      I know the 3" tailpipe are very snug going over a Dana 60, and by the gas tank. But they do fit.
                       
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                      • BSB67

                        BSB67 Well-Known Member

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                        There are guys making over 800 HP on stroked hemis with 2 1/2" exhaust systems. This is because the class rules require it. Certainly they'd do better with 3", but the point is that it is silly to think you need 3" for <600 HP street car unless you just want it loud.
                         
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                        • astjp2

                          astjp2 Well-Known Member

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                          So I guess the Pypes 3.5” X pipe will not fit well for my 572 Hemi? Should I go with th 3”? Power is estimated at 720. Car currently has hooker supercomp headers. And I am planning on a resonator and Dyno max mufflers.
                           
                        • 383man

                          383man Well-Known Member

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                          I run the TTI 3" full exhaust system on my 63 Sport Fury with the X-pipe and TTI 2" headers. Its fits my car just fine and has good room in the back as you can see. I don't think TTI would make and sell the 3" system if it would not fit but of course it may be tight. I also run Dyno-Max Ultra-Flow mufflers and its not that loud at all when at idle or cruising. Its a bit loud only when I lay into it but with my tailpipes all the way out the back it helps keep the noise down. My eng makes around 600 hp and it pushes my 63 in the 10's through this full exhaust as I race it just as I drive it. Myself I like the 3" X-pipe system because its not to loud for me and it still runs good when racing through the exhaust. Ron

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