340 HP's vs headers

Mopar Exhaust Systems

  1. moparmat2000

    moparmat2000 FABO Gold Member FABO Gold Member

    Messages:
    18,390
    Likes Received:
    7355
    Joined:
    May 13, 2010
    Location:
    Grand Tetons
    Local Time:
    4:35 PM
    I am back on the 408 stroker deal. I posted the temp use 318 deal on a different thread.
     
  2. 273

    273 Well-Known Member

    Messages:
    3,453
    Likes Received:
    1190
    Joined:
    May 14, 2012
    Location:
    Ontario
    Local Time:
    5:35 PM
    To kill a 150 hp on a 450 hp engine would back to stock 340 hp numbers. Air compresses my cousin's stock car engine pulls to 7000 rpm with a 2 bbl making well over 400 hp. Nascar makes 800 hp with restrictor plates with dime size holes.

    Obviously manifolds aren't the best idea for performance. But with a little planning can't see why you can hit your goal of 400+ hp.
     
    • Thanks! Thanks! x 1
    • toolmanmike

      toolmanmike FABO MODERATOR Staff Member FABO Gold Member

      Messages:
      56,943
      Likes Received:
      43503
      Joined:
      Jan 18, 2006
      Location:
      Iowa
      Local Time:
      4:35 PM
      I have been following this old thread you revived. I just bought a pair of early HP 340 manifolds. I would also like to liven up my 318 in my Swinger. I have a LD4B and a assortment of 600-650 cfm carbs. I would like to follow up with TTI exhaust or at least get the front pipes from them and finish out the exhaust. This combo seems to help the teen's performance. I may put in a little cam while I'm at it.
      I think with a stroker it would be best with headers of some kind. The engine is just a big air pump and a stroker uses quite a volume of it. It has to get out as fast as it came in. Keep us posted on what you do and the outcome. tmm
       
      • Like Like x 1
      • MopaR&D

        MopaR&D Nerd Member

        Messages:
        4,261
        Likes Received:
        1114
        Joined:
        Jan 4, 2008
        Location:
        Fort Collins, CO
        Local Time:
        3:35 PM
        Headers are more about tuning the exhaust pulses than overall flow capacity. There are some magazine builds out there where they added a set of longtube headers to a stock 300-HP 5.9L Magnum crate engine and it picked up like 3 HP. Put the same headers on the 380-HP crate with the big cam and it's more like a 20-30 HP boost even though the displacement is the same. I liken it to tuning a 2-stroke; when you have both the intake and exhaust passages open to the cylinder at the same time (like in a 2-stroke or a 4-stroke engine with a high-overlap cam) the ability of the high-inertia exhaust gases to move quickly out of the cylinders and help pull more fresh intake charge into the cylinder is critical. A 408 stroker will work fine with manifolds, you just have to build the engine with that excessive high-RPM backpressure in mind so it will (in my mind) need a short-duration split-pattern cam with extra lift and duration on the exhaust side compared to intake. Also check out the episode of Engine Masters where they bash a set of headers to oblivion and it didn't affect HP at all, showing that the length and overall diameter of the tubes is way more important than the actual cross-sectional area of the tubes which is what everyone intuitively points at for making more power (bigger tube=flows more air).

        Comparing it to intake restrictor plates isn't quite the same because in reality those NASCAR engines take advantage of the massive negative pressure exhaust pulses produced by the tuned headers to pull air through those tiny intake holes as hard as possible. When you mess with the exhaust side and take away that tuned scavenging affect it throws everything out of whack and kills massive amounts of HP. Granted most of what I'm saying comes from literature (David Vizard's How to Build Horsepower) not from my own testing unfortunately.
         
      • moparmat2000

        moparmat2000 FABO Gold Member FABO Gold Member

        Messages:
        18,390
        Likes Received:
        7355
        Joined:
        May 13, 2010
        Location:
        Grand Tetons
        Local Time:
        4:35 PM
        Got a set of hedman block huggers coming. I will make my own downpipes. Off thesr while on my 318 mockup motor.

        The 318 runs great, and is stock, i will prob do what others have mentioned, and put a good timing chain on it, install those 340 exhaust manifolds on it, get an LD4B and an eddy 600 and drop it in my kids car. For now it will still be doing mockup duty for the downpipes for this car.

        Anybody know where i can get 2&1/2" diameter muffler tube mandrel bends that i can cut apart and make my own down pipes out of. I'm thinking i can do this, and buy the header type exhaust kit from summit, and add another set of collector flanges to tie it together.
         
      • MopaR&D

        MopaR&D Nerd Member

        Messages:
        4,261
        Likes Received:
        1114
        Joined:
        Jan 4, 2008
        Location:
        Fort Collins, CO
        Local Time:
        3:35 PM
        You're definitely gonna need a pair of these: Header Reducer Set, Angled There's simply not enough space to have straight collectors and try to have the pipe go back up and over the steering linkage, at least with my stock stuff. I'm a little leary of changing the pitman and idler arm lengths because that might screw with the steering geometry (bump steer etc.). I also had to use one of those premade exhaust pipe "donuts" like this one, only way to get tight enough bends for it all to fit: Mandrel Bend Donut 2.5" 2.50" 2.5in 2.50 2.50in Exhaust Intake Stainless Steel | eBay
         
        • Thanks! Thanks! x 1
        • moparmat2000

          moparmat2000 FABO Gold Member FABO Gold Member

          Messages:
          18,390
          Likes Received:
          7355
          Joined:
          May 13, 2010
          Location:
          Grand Tetons
          Local Time:
          4:35 PM
          Aaaah the donut. And just cut pieces out to make a tube wedges and weld em up. The angled collectors will definitely help. Thanks for showing me those Khalid. I never knew those existed. I guess i got to get the headers mocked up on the teener under the hood first, and then see where to go from there. My chuck is filthy, and i just had lower back surgery 3 weeks ago, cant lift over 10lbs yet so i'm not moving it around to clean it up and temp install it just yet. At least not till i get a clean bill of health from the doctor.

          The longer pitman and idler arms only mess with ackerman angle when steering wheel is in full lock. Thats only going to happen when parking it. No bump steer issues. This was how Chrysler got fast ratio steering on the T/A challenger and AAR cuda back in the day, no joke. Old racers trick. You do that, and use the pressure valving off a slant sux saginaw pump, and lower the line pressure, and you get a fast ratio steering chuck that feels like a rack n pinion. Problem w moving center link back is certain long tube headers tend to not fit, but this may make a little more room to augment the header downpipes
           
          • Like Like x 1
          • MopaR&D

            MopaR&D Nerd Member

            Messages:
            4,261
            Likes Received:
            1114
            Joined:
            Jan 4, 2008
            Location:
            Fort Collins, CO
            Local Time:
            3:35 PM
            Cool good to know about the steering, I know the AAR-T/A cars had something like that but I didn't realize it was that simple. I put one of the Firm Feel Stage 2 P/S boxes in my Duster, with that, smaller steering wheel and proper caster at the wheels it felt like a modern car. I remember showing it to an older friend of mine (relatively, I'm 26 he was like 53?) and he was shocked by how much better it felt than stock steering, he had never experienced a Mopar with that kind of steering feel with "stock" components.
             
          • moparmat2000

            moparmat2000 FABO Gold Member FABO Gold Member

            Messages:
            18,390
            Likes Received:
            7355
            Joined:
            May 13, 2010
            Location:
            Grand Tetons
            Local Time:
            4:35 PM
            I think the plan for the teener will be the LD4B, a eddy 600 and those 340 hi po mannys, and some 3.73s in a 69 notchie. That should be plenty for a teenaged driver.
             
            Last edited: Oct 12, 2017
            • Like Like x 2
            • Agree Agree x 1
            • moparmat2000

              moparmat2000 FABO Gold Member FABO Gold Member

              Messages:
              18,390
              Likes Received:
              7355
              Joined:
              May 13, 2010
              Location:
              Grand Tetons
              Local Time:
              4:35 PM
              Yep they were sloppy as heck back then. About half the problem is the way overboosted assist. Dial the line pressure down a bit and it tightens up. I think in a mopar action article they said its about 1,600 psi stock, and dialing it down to about 850 psi. tightens it up. Not 100% on the numbers though. Find the article on the net, and check it out.
               
            • moparmat2000

              moparmat2000 FABO Gold Member FABO Gold Member

              Messages:
              18,390
              Likes Received:
              7355
              Joined:
              May 13, 2010
              Location:
              Grand Tetons
              Local Time:
              4:35 PM
              Well in another thread similar to this one , and this one i mentioned that i hate headers, but pulled the trigger on these shorties. So i guess i'm gonna eat crow over this one. Maybe these are better made. I will use copper gaskets. Guess i will find out.
               
            • MopaR&D

              MopaR&D Nerd Member

              Messages:
              4,261
              Likes Received:
              1114
              Joined:
              Jan 4, 2008
              Location:
              Fort Collins, CO
              Local Time:
              3:35 PM
              The Hedman Tight Tubes are good quality, head flanges are nice and thick I believe 3/8", tubes are pretty thick gauge steel and the welds are nice too. The driver-side fits nicely around power steering stuff, they also come with some nice small-head bolts that use like a 3/8" wrench. IIRC I used the gaskets that came with the headers from Hedman and sprayed them with copper sealant then tightened the header bolts evenly bit-by-bit. NEVER had a leaking issue after initial install and I put 25k hard miles on that 360 until it kicked the bucket (tuning errors, too much detonation). Main downsides were the exhaust routing which it sounds like you got covered, and high underhood temps but that happens with any uncoated headers, unless you got coated ones?
               
            • moparmat2000

              moparmat2000 FABO Gold Member FABO Gold Member

              Messages:
              18,390
              Likes Received:
              7355
              Joined:
              May 13, 2010
              Location:
              Grand Tetons
              Local Time:
              4:35 PM
              I may either get em jet hot coated in dark gray, or wrap em in header wrap.
               
            • moparmat2000

              moparmat2000 FABO Gold Member FABO Gold Member

              Messages:
              18,390
              Likes Received:
              7355
              Joined:
              May 13, 2010
              Location:
              Grand Tetons
              Local Time:
              4:35 PM
              I think i did pretty good on those hedmans today actually. A guy had em on evilbay for $175 with an awful silver spray job on em. Said he ran em on a dyno on his small block, then went big block. I offered and got them for $150 shipped. I will sand blast em at work, and spray em w a high heat coating.

              Screenshot_20171013-053500.png
               
              Last edited: Oct 13, 2017
            • 318willrun

              318willrun Utube channel 318willrun

              Messages:
              16,332
              Likes Received:
              18052
              Joined:
              Sep 13, 2013
              Location:
              I'm here
              Local Time:
              4:35 PM
              LOL... I didn't realize this thread was old. I was answering the original OP's question.
               
            • moparmat2000

              moparmat2000 FABO Gold Member FABO Gold Member

              Messages:
              18,390
              Likes Received:
              7355
              Joined:
              May 13, 2010
              Location:
              Grand Tetons
              Local Time:
              4:35 PM
              Its all good, i forgot it was someone elses thread lol. I will still be doing the bit to the 318, but now will put it in my sons car when we build that project. An LD4B is a pricey vintage piece now, an i see em with a bunch of corrosion in the water jacket areas, so hows a Weiand stealth stack up against it? I kinda like squarebore manifolds myself, i think the eddy performer is a spreadbore.
               
              Last edited: Oct 13, 2017
            • 318willrun

              318willrun Utube channel 318willrun

              Messages:
              16,332
              Likes Received:
              18052
              Joined:
              Sep 13, 2013
              Location:
              I'm here
              Local Time:
              4:35 PM
              Ok, I didn't go back and see what all your plans are for the 318, but in comparison to the LD4B, I think the Weiand Action Plus is a great intake for 318's. They do have a spread bore design, but a square bore carb bolts straight on top of 'em. I like them better than the eddy performer. Pretty easy to get second hand, and cheaper to buy brand new. Great intake on a stock 318, and a great intake on a 318 with a mild cam, headers, and some head work including 340/360 heads.
               
            • moparmat2000

              moparmat2000 FABO Gold Member FABO Gold Member

              Messages:
              18,390
              Likes Received:
              7355
              Joined:
              May 13, 2010
              Location:
              Grand Tetons
              Local Time:
              4:35 PM
              Engine ran great out of 74 dart parts car. No smoke, didnt knock, decent oil pressure. I was gonna change seals, gaskets, core plugs, water pump, clean out and reinstall the oil pan. Add 340 exh manifolds, and a nice aluminum intake with a 600 carb, electronic ignition w GM HEI.
               
            • 318willrun

              318willrun Utube channel 318willrun

              Messages:
              16,332
              Likes Received:
              18052
              Joined:
              Sep 13, 2013
              Location:
              I'm here
              Local Time:
              4:35 PM
              If you are not going to do head work or swap cams, then a lot of intakes would do you great service. Here is a short list of easy to find and easy on the wallet, but there are others as well:
              1. Factory Cast 4 bbl
              2. Old Holley Street Dominator (I just bought one for 30 bucks). I'm talking the one without the divider in the plenum
              3. Edelbrock performer
              4. Weiand Action Plus
              I would suggest putting new valve seals in as well. Those LA small blocks are great for having them get brittle. Then you smoke when you start up, or idle for a while at a stop light. Also, all those brittle, broken valve seals end up in your oil pickup screen.
               
            • H22A4

              H22A4 Does anyone read this?

              Messages:
              2,216
              Likes Received:
              1103
              Joined:
              Aug 4, 2006
              Location:
              YVR
              Local Time:
              2:35 PM
              If you're patient you should be able to find a LD4B at a reasonable price (less than $200). Most of the ones on eBay now start at $200 or $250 and still need work. Clearly some folks are paying that amount for LD4B's since most of them are not relisted.
               
            • moparmat2000

              moparmat2000 FABO Gold Member FABO Gold Member

              Messages:
              18,390
              Likes Received:
              7355
              Joined:
              May 13, 2010
              Location:
              Grand Tetons
              Local Time:
              4:35 PM
              I dont mind a weiand action plus, or a street dominator. Will need to hit next swap meet and look 4 one.
               
            • H22A4

              H22A4 Does anyone read this?

              Messages:
              2,216
              Likes Received:
              1103
              Joined:
              Aug 4, 2006
              Location:
              YVR
              Local Time:
              2:35 PM
              One of the Weiand's is almost an exact copy of the LD4B but I dont recall which one. I looked at buying a new Weiand if I couldn't get a good deal on a LD4B.
               
            • 318willrun

              318willrun Utube channel 318willrun

              Messages:
              16,332
              Likes Received:
              18052
              Joined:
              Sep 13, 2013
              Location:
              I'm here
              Local Time:
              4:35 PM
              why people over pay for the LD340/LD4B is beyond me, unless they want the retro-old school look (which I understand). Plenty of intakes that will match or exceed them for less money.
               
              • Like Like x 1
              • Agree Agree x 1
              • moparmat2000

                moparmat2000 FABO Gold Member FABO Gold Member

                Messages:
                18,390
                Likes Received:
                7355
                Joined:
                May 13, 2010
                Location:
                Grand Tetons
                Local Time:
                4:35 PM
                It doesnt have to be an LD4B. It can be something that flows just as good. Maybe a weiand action plus will fit the bill.
                 
                • Agree Agree x 1
                • myduster360

                  myduster360 Well-Known Member

                  Messages:
                  581
                  Likes Received:
                  757
                  Joined:
                  Oct 8, 2009
                  Location:
                  North Mississippi
                  Local Time:
                  4:35 PM
                  Everyone thinking about if headers are "worth it" needs to get this "HEADER DESIGN INFOPAK" from Headers by Ed
                  I first ordered it over 25 years ago. It was the most eye opening, practical advice on testing and design I've ever heard. I can even say it played a part in inspired me to go into Mechanical Engineering.

                  Get More Header Design & Construction Information
                   
                1. This site uses cookies to help personalize content, tailor your experience and to keep you logged in if you register.
                  By continuing to use this site, you are consenting to our use of cookies.