dutra manifolds vs header

Slant 6 Engines

  1. vitamindart

    vitamindart Well-Known Member

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    I am looking into a turbo build for my slant. would there be any benefit or drawback to the dutra manifolds vs a custom header? was thinking the manifolds would be a little easier to plumb up vs making a whole header. possibly less likely to leak as well.

    thanks!
     
  2. my68barracuda

    my68barracuda Well-Known Member

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    I have a set of Dutra’s on the slant in the D150, and yes it would seem that Dutra’s would flow better than a stock exhaust manifold, but also consider:
    1) Dutra’s are really heavy, they are thick cast iron, will last for ever but weight about the same as a stock exhaust manifold.
    2) For all the money that you will spend to get a set of Dutra’s, you really only have the first couple of inches of an exhaust system.
    So if you can weld, it may be less expensive to buy a slant six header flange from eBay then make your own custom turbo exhaust. If you don’t know how to weld and you will be paying someone to fabricate it for you, I would have the fabricator price it both ways, 100% custom fabrication vs adding on to twin Dutra’s.
    If I was going to turbo a slant six I think I would port-polish-clean up a stock slant exhaust manifold and make a simple J pipe to connect it to the turbo and use the money saved to spend on improved: ignition-timing-fuel controls.
     
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    • vitamindart

      vitamindart Well-Known Member

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      the real kicker is I have a header flange, was just questioning the durability and extra work of the header vs the Dutra's. i dont know that the stock manifold will get me the end result Im looking for, plus I have replaced more than a few cracked stock manifolds. it does give me another option to ponder.

      the car will be going multiport injection with coil on plug ignition ( i should have listened to your advice when i was on the fence about TB vs multiport )
      could have saved some time and just done it once.
       
    • my68barracuda

      my68barracuda Well-Known Member

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      The best guy that I know when it comes turbo slants is Charlie S. He frequents FABO, if he does not chime in I will ring him.
      @Charrlie_S
       
      Last edited: Feb 18, 2021
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      • RustyRatRod

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

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        Headers will beat manifolds every single time for performance. Now for longevity, manifolds, hands down. But remember, with Dutra's manifolds, you are cutting out the hot air to the intake. So if you live in a cold area you may regret it.
         
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        • RustyRatRod

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

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          He's a legend for sure and most people don't even know it.
           
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          • vitamindart

            vitamindart Well-Known Member

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            Im not worried about the heat, the car currently has headers and no intake heat. Once the real cold sets in the car gets put away. Going port injection should also eliminate the need for manifold heat.
             
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            • Killer6

              Killer6 Well-Known Member

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              It depends on what output level & driveability You want, but most street apps are better served with a compact & direct manifold, lag is reduced with varying operating conditions. A heavy cast manny holds heat in between romps & won't suck the thermal energy out of the exhaust gasses on the next romp as much, & the bigger the rest of the downstream piping the better. Most new engines are 1 piece turbo/mannys, or there aren't even mannys at all, ports merge in head to a rectangular flange...turbo right off head. I've been giving the Ford Ecoboost F150 units some scrutiny, they are unique in form & design, &diff side to side. They may be able to be fitted to Dutras, & sized just right, controlling them may be a challenge tho'. I'd like to get a pair & investigate further.
               
            • diymirage

              diymirage HP@idle > hondaHP@redline

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            • Charrlie_S

              Charrlie_S Well-Known Member

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              Exhaust really depends on what you are after. As a reliable street driver, or a race car, or something in between. Budget plays a big part. For a street car, Dutra duals would probably be best, with a common pipe to the turbo. That will be pretty pricey. For a race car, headers to the turbo, again fairly pricey, custom work. For a street car at low(er) boost levels, a "J" pipe off a good quality stock type manifold works fine. One important thing to remember, and I never see it mentioned. Support the turbo. Don't expect the exhaust plumbing to do the job. Also don't skimp on the exhaust out of the turbo. Back pressure is not your friend.
               
            • vitamindart

              vitamindart Well-Known Member

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              killer,
              that is about what i was thinking just with a single turbo. i have an offy intake getting injector bungs welded into it. ( figured the shorter manifold would give me more room )

              charlie, we are trying to get that middle road, not a racecar not a driver somewhere in between. hoping maybe I can recoup some of the cost of the Dutra's when I sell my clifford headers.
               
            • vitamindart

              vitamindart Well-Known Member

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              alright, just pulled the trigger on a set of Dutra's, hoping to have them, my intake back and the MS3 in a few weeks. I will do my best to document the progress and start another thread. hoping this doesnt completely kill my summer cruising with the car.
               
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              • my68barracuda

                my68barracuda Well-Known Member

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                On the set of Dutra’s on the slant on my D150. Between the cylinder head and the Dutra’s I have not had any issues using a stock Felpro gasket. I did have the machine shop take a very light skim cut on the manifold face of the head so it is clean and flat. However from the Dutra’s exhaust exit to the flanges on the exhaust pipes, over the counter two bolt bolt gaskets do not last. They will be good for a couple of thousand miles then burn through and develop an annoying exhaust leak. After changing those out the second time I put in a Remflex two bolt hole gasket and it has been fine for over 35K miles. It’s either the exhaust exit on the Dutra’s or the flanges on the exhaust pipes that have an issue but the Remflex gaskets handle it.
                 
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                • vitamindart

                  vitamindart Well-Known Member

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                  thanks for the heads up, need to get them in hand to decide how to make the connections. may make it a 2 step process and get it running without the turbo first. just not sure i want to do that exhaust twice.
                   
                • my68barracuda

                  my68barracuda Well-Known Member

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                  With the studs on the ends, the slant cylinder head was designed for a one piece exhaust manifold. The Hooker Headers that I run on the slant in the 68 Barracuda are a two piece design like running dual Dutra’s. When installing the Hookers, It took time to center both exhausts and the intake on the ports with the engine in the car.
                  What I did was, one time when I had the motor out and on a stand, I aligned the exhaust and intake manifolds on the head port openings perfectly, tightened them down then drilled a pilot hole through each exhaust flange into the manifold face, being careful to not drill into the water jacket. Removed the manifolds and put a roll pin in each pilot hole drilled into the head manifold face. I enlarged the through holes in the flanges slightly so they are an easy slip fit. Now when assembling the manifolds to the engine in the car, it is easy to get the exhausts in the optimum position. Next time I have the engine out of the D150 I will do something similar with the Dutra’s.
                   
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