Stock 340 Manifolds or TTI Shorties?

Mopar Exhaust Systems

  1. Ricks70Duster340

    Ricks70Duster340 Child of the King FABO Gold Member

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    I have a new Blueprint Engines 408 and currently am using the original 340 manifolds. I bought TTI 1 5/8" shorties for the project but am rethinking my decision to install them. Anyone have experience with performance improvements between the two? The car will be used on the street only and max RPM 5500. Car has 3.23 gears with 28" tires and a PTI 3000 stall converter. Thanks guys.
     
  2. tubbedamx

    tubbedamx Location Boise, Idaho

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    I'm struggling with the same decision. I have a little less engine and converter but I am using a magnum manifold on the passenger side and a HP340 on the drivers side with TTI 3inch full exhaust. Curious what others have to say.
     
  3. fklskv

    fklskv Well-Known Member

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    Swapped out manifolds for long tube TTI’S. On the street you will find no difference.
     
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    • cpearce

      cpearce Well-Known Member

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      Is this a statement of results, or opinion? I find it hard to believe no difference would be noticed on a stroker going from cast manifolds to headers. On the dyno my 408 made 25 more horsepower going from 1 5/8 headers to 1 3/4 headers. I'm pretty certain 25 hp can be noticed, manifolds to headers likely a bigger gain.
       
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      • Ricks70Duster340

        Ricks70Duster340 Child of the King FABO Gold Member

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        Was the dyno run through mufflers, or open? On the street, the exhaust is bottled up so that would likely negate some gain. I don't mind installing the shorties if they will provide a notable gain, but is it worth the effort and need to go back to the exhaust shop to have them join the existing exhaust to the new headers? That is my question. Also, I am running the 1970 340 manifolds if that makes any difference.
         
      • toolmanmike

        toolmanmike Moderator Staff Member FABO Gold Member

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        Do the shorties even fit?
         
      • cpearce

        cpearce Well-Known Member

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        The dyno test merged the collectors into one huge muffler outside of the building. As far as manifolds are concerned the 340 ones are good, but they were good on 340ci. You are now displacing 408ci, so by increasing the displacement you are now asking the air pump(engine) to pump more air, but restricting the outlet by pinching it off. It doesn't seem like a good fit to me, unless it is required for a class like F.A.S.T.. Additionally, I would think your 408 will produce more heat than the 340 did, cast manifolds act as a big heat sink right at the head, you will get this heat away easier with headers.
         
      • Ricks70Duster340

        Ricks70Duster340 Child of the King FABO Gold Member

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        I did a test fit when I installed the engine, and yes they do.
         
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        • Ricks70Duster340

          Ricks70Duster340 Child of the King FABO Gold Member

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          Good point. The TTI headers have a coating that should reduce underhood temps as well.
           
        • fklskv

          fklskv Well-Known Member

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          Manifolds on the track 9.1 in 1/8. Headers open 8.5 open, 8.7 closed. On the street those differences are basically nil, that is unless you plan on racing from every red light.
           
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          • cpearce

            cpearce Well-Known Member

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            Thanks for reply, I must say, I find these results surprising. This was a 408?
             
          • Ricks70Duster340

            Ricks70Duster340 Child of the King FABO Gold Member

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            Wonder if Johnny Mac has any thoughts on this? @Johnny Mac
             
          • 6PakBee

            6PakBee FABO Gold Member FABO Gold Member

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            When I was young I loved headers. Put up with the continuous gasket leaks, lack of spark plug access, difficulty in changing starters, burnt spark plug wires, smashed tubes; I was young. Now, everything I have has the stock manifolds. Your priorities change over the years.
             
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            • Ricks70Duster340

              Ricks70Duster340 Child of the King FABO Gold Member

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              You are right, and I too have been there. The big difference here is these headers are the shorties. The long tube headers were the real pain for me. These headers have great plug access and should provide good clearance to the (mini) starter I have. I have done so many engines in the past that I do not recall specifics, but I used Hedman a lot back in those days. We have options today that were not available back then. For that I'm grateful!
               
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              • Johnny Mac

                Johnny Mac www.blueprintengines.com FABO Vendor

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                I think this is a "do what makes the most sense for you" scenario. If you are only driving this on the street...can you feel the approximate 20 top end HP that shorty headers may gain vs manifolds? The engine will certainly breath better, but at the same time, if that takes you a weekend, and several hundred bucks in getting exhaust re-done...then thats your call. I'd make the same contemplation if it was worth the time and money. Now if we're talking manifolds to long tubes...yes I 100% believe THAT would be worth it. If you see any strip action, assuming you hook...I'd guess manifolds to long tubes may gain you a few tenths. manifolds to shorties...probably 1/2 of that gain, but also depends on how much the manifolds are choking it. I have never "bothered" putting shorties on anything in my life, and probably never would unless they were cheaper than a replacement manifold, and i had a cracked one or something. if you're going to the trouble to install headers, i'd go long tubes. Now if those are those TTI Tri-Y things...those are closer to a long tube than a shorty...so if you have them, i'd probably throw them on.

                Kinda rambled above, but I hope it helps.
                 
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                • Johnny Mac

                  Johnny Mac www.blueprintengines.com FABO Vendor

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                  you're correct...most long tubes in an A-Body aren't much fun to install. Between the drag link going between the tubes...the low ground clearance...having to take the engine lose. But on the flip side, some of the $ versions that don't go through the drag link, cook the starter. It's a balancing act. Yay hotrodding :)
                   
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                  • Ricks70Duster340

                    Ricks70Duster340 Child of the King FABO Gold Member

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                    Thanks for the comments. Yes, now decisions, decisions....
                     
                  • Brooks James

                    Brooks James VET, CPT, Huey Medevac Pilot FABO Gold Member

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                    I researched the same, it all depends on the compression, tube size, cam,intake,heads etc. I found that for street engine 10-20 hp. I also saw a dyno test on a street small blocks where 1 5/8 street headers only had 8 hp Over 68-71 340 manifolds
                     
                  • pishta

                    pishta I know I'm right....

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                    shorties dont have a proper collector, that is a key feature for the scavenging effect of a header that would normally lean out a motor as a side note. 340 logs or big magnums for a street car over shorties that neck down to a 2.5 or less right at the merge. Applications are different. some are worse that others.
                     
                  • abodyjoe

                    abodyjoe Well-Known Member

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                    not an issue these days with dougs and tti.. :)
                     
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                    • abodyjoe

                      abodyjoe Well-Known Member

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                      i think that right there says the manifolds will be fine for what you are doing.. shorty headers are like being a little bit pregnant aren't they?
                       
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                      • 69_340_GTS

                        69_340_GTS Well-Known Member

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                        The TTI shorties fit almost perfect, and will not leak. They make a nice, quality header. But you'll really need the TTI headpipes that go with them. Only place I had fitment issues was at the kickdown linkage on the transmission. It's pretty easy to modify, or just use a Lokar kit. I have no idea on the performance. I never had a chance to compare them to stock manifolds.
                         
                      • Ricks70Duster340

                        Ricks70Duster340 Child of the King FABO Gold Member

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                        Thanks. I already have the Lokar kit installed. Only other deviation from stock is I plumbed the cooler lines with -6AN braided hose because the original lines were bad.
                         
                      • AAndrews

                        AAndrews MOPAR .. Move Over, Plymouth Approaching Rapidly!

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                        340 Mild build and now Stroked 360 Magnum. Had stock 68 manifolds, long tube headers and now using TTi shorties. Long tube had best performance, Manifolds had most leaks, mostly due to mods done to choke (my fault) .Shorties are proving most liveable as plug change is easier no denting tubes to fit and underbody clearance with a 4-speed is much better as I can tuck exhaust up much higher. No more scraping! All depends where you want to compromise.
                         
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                        • toolmanmike

                          toolmanmike Moderator Staff Member FABO Gold Member

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                          ...

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