340 HP's vs headers

Mopar Exhaust Systems

  1. Saetun

    Saetun Sinister Swinger

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    I've got a 318 w/ 2 1/4" duals with stock 73 318 manifolds. I'm getting ready to finish my build & am weighing the options of 340H.P. manifolds vs. traditional headers. I'm not sure that $600+ TTI headers are in my future but I may be able to pull together enough for the Hi-po manifolds or headers with a less than ideal fit. I'd appreciate some folks talking through the pros & cons of my options. Thx.
     
  2. crackedback

    crackedback FABO Gold Member FABO Gold Member

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    Dougs are a lower cost alternative to tti as a good fitting header.
     
  3. Saetun

    Saetun Sinister Swinger

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    No one has anything good to say about the 340 hp's? Hoping someone could share their opinion/experience with both options.
     
  4. 1968FormulaS340

    1968FormulaS340 Well-Known Member

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    It really depends on your build level. If your 318 is a high RPM screamer you will be giving up more than is it's only a 5,500 RPM street machine.

    I know for a fact you can run at least in the 12s through the HP manifolds, if that helps.
     
  5. RustyRatRod

    RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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    MRL just did a comparison between HP and stock manifolds on a mild big block and there was NO difference at all. Between manifolds and headers, as he said, I suspect the headers would surely win out.
     
  6. forphorty

    forphorty Well-Known Member

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  7. RustyRatRod

    RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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    No offense, but magazine articles would be the last thing I'd trust. They have sponsors. lol
     
  8. 340sFastback

    340sFastback Well-Known Member

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    340 manifolds, the '69-'70 models, are going to flow a lot more than stock 318 manifolds. But they are not cheap. For around the same money you can get a set of Dougs headers. But if you go with 340 manifolds and want to upgrade to headers later you most likely get your money back out of them. The other thing about 340 manifolds is you will need different head pipes where as if you with Dougs you would be able to hook your current system to the headers without much trouble.
     
  9. waggin

    waggin moving on ain't easy if you drive a Ford :p

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    try 5% more performance from race headers over the 340 hp manifolds say's mullen & co.
     
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    • RustyRatRod

      RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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      After seein the dyno numbers from MRL on his big block, I'd have to see the proof.
       
    • Saetun

      Saetun Sinister Swinger

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      With long tube headers like Dougs, TTI, etc... What can I look forward to as far as mods to the current exhaust setup I've got. Which is true duals from the manifolds back. I guess I'm trying to figure out after I mount the headers (or 340 manifolds) how do I tie it in to my existing system. Will the exhaust shop just cut the down pipes to right length & weld in? Sorry for the rookie questions.
       
    • waggin

      waggin moving on ain't easy if you drive a Ford :p

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      I'm not diggin thru the attic for the book, -5% performance = - the headache of blown header gaskets, - the pain in the ass to replace starter motor, - the cost of mini starter to avoid that, - the steering linkage issues and all the other things, although I have headers on my duster and none of them issues, if I didnt have the headers layin around I would have used the 340 hp manifolds as I have done in the past.......Just Sayin :happy1:
       
    • Saetun

      Saetun Sinister Swinger

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      Great point & something definitely worthy of some thought & discussion. 340 HP manifolds also seem to be trading a little less than they have in years past I'm sure in no small part to hard times.
       
    • RustyRatRod

      RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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      I didn't see anybody askin you to dig. Who was arguin with you?
       
    • Johnny Dart

      Johnny Dart Well-Known Member

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      I would say you would be losing right around 10-15 horse with the 340 manifolds vs Doug's or TTI's.
      Having said that,I had a 1970 318 dart with 340 manifolds,dual exhaust,4 bbl that ran awesome. Plus they are a cinch to install and maintain. Accurate exhaust sells head pipes to help with instalation. But as mentioned,340 manifolds are pricey. Really just depends on what direction you want to go.
       
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      • 340sFastback

        340sFastback Well-Known Member

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        What the power difference is between 340 manifolds and headers will vary dramatically depending on the engine. If its a stroker with big cam and fully ported heads you will be giving up a ton of power with the manifolds. If its a mild 318 probably would not be very noticeable.

        The Doug and TTI header collectors line right up with the two humps in the trans cross members which is probably where your existing exhaust is routed. The cheap headers do not line up.

        And like waggin says, you will probably want to run a mini starter with headers. If you have a pick and pull junk yard in your area you can get one off a Dakota for cheap. But yeah headers can be a pain to get installed and they make working on the car difficult at times.

        If you want max performance or think you will do an engine upgrade later go with headers. If you want easy maintenance and are willing to give up a little power go with 340 manifolds. If your 318 is mild I don't think you will be losing any noticeable power with the manifolds.
         
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        • jerry6

          jerry6 Banned

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          you can always go the hedman tight tube route , cheap , easy to install , no problems getting the starter or plugs , and make good power . I have them on my 70 340 and car runs faster than with the old hooker headers . Hardest part wart routing form collectors to exhaust . Hve yet to bottom out and mine are routed ubder the steering . There are oics in other threads , also txstang has them routed above steering so really good clearance .
          Of course mine is a mild build 413 hp 398 torque , so headers help over manifolds .
           
        • pishta

          pishta I know I'm right....

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          Screw them all and run early magnum truck logs. 2 1/4(?) outlets and they flow great...and can be had for $50 a pair. 5% is margin of error on a dyno and header headaches are real, lots of heat, lots of leaks and lots of rust issues..oh did I day ground clearance? Last time I saw nice 340 Hi-po's ther were 4-600 by themselves. Too much, people are very proud of those logs...Now if it is a built motor, headers will add serious HP but on a stocker, niet.
           
        • Saetun

          Saetun Sinister Swinger

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          This is an interesting option which I'd like to know more about. Does anyone else have any insight on the tight tube headers? My setup is currently a stock 318 with a Holley 600 vac on and Performer intake & 2 1/4" dual pipes. Cam is going in this summer & looks like it will be 224/230 @ .050 w/ .477/.480 or 218/224 @ .050 w/ .462/.470. looking to reach somewhere around 280-300hp range nothing radical. I do have power power steering will that make a difference in what will fit? Will I still need to change to the mini starter for clearance?
           
        • 68gtxman

          68gtxman I used to reMember

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          Does anyone have a set of 340 exhaust manifolds for sale? I am swapping a 340 for my 1967 Cuda's 273 factory setup. I'd like to keep the factory look and I am guessing that the 273 logs won't be useable - right?
           
        • 65Vart

          65Vart Well-Known Member

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          I traded a 8 3/4 3.55 center for a set of 340 manifolds (68-70) . Steve(4spdragtop) aced them up with a blasting and POR15 treatment. They look mint. I plan to run them on my 318 with the exhaust system from TTI on my 71 swinger until i get a real motor for the car . The rear end was a 741 so I think I did ok (even trade). Ive had headers on lots of street cars. If these mannis work as good as I am told it's a good trade off for the leaks and the hassles that come with cheap headers.........I must be getting old:D
           
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          • Johnny Dart

            Johnny Dart Well-Known Member

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            I talk about this set-up alot when this question comes up.
            This was a stock 60,000 mile 318 in a 70 Dart.
            Added the following:
            Ede Performer
            Ede 600
            340 manifolds
            Dual exhaust H-pipe
            Electronic ignition.
            Little shit ran like gangbusters !!!! :burnout:

            View attachment Picture 498.jpg
             
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            • 340sFastback

              340sFastback Well-Known Member

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              If you get TTI exhaust for the 340 manifolds the head pipes are 2 1/2" right off the manifolds with no pinches.
               
            • 65Vart

              65Vart Well-Known Member

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              Yup, have to buy TTI tips as well I hear.
               
            • dustoff440

              dustoff440 Well-Known Member

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              I was in the same sit as you with a warmed over 360 MAgnum, Dyno tests have shown 20-25 horsepower where headers are put on a pretty much stock 340 the better headers (tti) had about 5 horsepower over cheaper ones. Your 318 build will not garner as much horsepower as the 340. The stock 340 manifolds 68-71 will give 11 horsepower over 318 manifolds. With 20 xtra horsepower you are not going to set the world on fire. 20 hp is only 2/10 in the 1/4 mile. If you already have a set of manifolds I would say run them, if not spend 150 bucks and get the Summitt headers.

              http://www.forabodiesonly.com/mopar/archive/index.php/t-12000.html

              http://www.moparts.org/Tech/Archive/exhaust/9.html

              http://www.moparchat.com/forums/archive/index.php?t-76417.html
               
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