340 exhaust manifolds

Magnum Engine Swaps

  1. ed1946

    ed1946 FABO Gold Member FABO Gold Member

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    Which set of 340 exhaust manifolds work best for the magnum swap. There appears to be several versions of these manifolds. Does the drivers side one that exits right top rear the best. A pic of what you used would help.
     
  2. 72Dart6pack

    72Dart6pack Well-Known Member

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    What are you putting it in? A John Deere tractor? Question is too vague.
     
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    • ed1946

      ed1946 FABO Gold Member FABO Gold Member

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      72 dart
       
    • pishta

      pishta I know I'm right....

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      • ed1946

        ed1946 FABO Gold Member FABO Gold Member

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        would these work for installing 360 magnum in 72 dart, has power steering
        these are off 318
        318 manifolds.jpg
         
      • pishta

        pishta I know I'm right....

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        ports will be too small and may not even seal with 360 gaskets. Use 318 gaskets but your leaving power on the table. Id go with Magnum logs, they are inexpensive, sized right and flow well. custom head pipes...or get them off the truck youll pull them from. Its a start.
         
      • 512Stroker

        512Stroker We are all here because we are not all there.

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        I have a couple sets if you need them.
        I dont know if they are the "best" but they will work and they are cheap$
         
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        • ed1946

          ed1946 FABO Gold Member FABO Gold Member

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          sent message via conversation
           
        • RustyRatRod

          RustyRatRod Weenie idiot loser. FABO Gold Member

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          @Treblig can probably help you decide. I tagged him so maybe he'll get in here.
           
        • Treblig

          Treblig Well-Known Member

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          The best flowing combination would be a 70s 340 driver's manifold and a Jeep Grand Cherokee (96/97/98) passenger's side manifold. This would give you the best flow for the lowest price. You can find a Cherokee manifold here:

          Car-Part.com--Used Auto Parts Market

          You can have it list manifolds by price or distance.
           
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          • ed1946

            ed1946 FABO Gold Member FABO Gold Member

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            Thanks for all the help. Have bought a set off 512Stroker, on to the next hunt.
             
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            • ed1946

              ed1946 FABO Gold Member FABO Gold Member

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            • ed1946

              ed1946 FABO Gold Member FABO Gold Member

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              received today, look good, thanks elmer
               
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              • DionR

                DionR Well-Known Member

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                Be aware that the 340 manifold port can be too large for the Magnum head. I have the MP R/T heads on my motor with 340 manifold both sides and I have to run an adapter plate between them to have a chance for them to seal.

                The reality is, I think the Magnum uses a 318 exhaust port size, or at the least is smaller then the 340/360 ports. They don't drop down on the bottom as much.

                Part of the issue is whether the Magnum head has extra material below the port. Mine doesn't and the manifold opening starts almost exactly where the material on the head ends. This leaves a small window at the bottom of the port where there is no crush on the gasket.

                5.9magnum questions

                Parts 018.jpg
                 
              • Treblig

                Treblig Well-Known Member

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                I have found that the magnum port matches the 340 exhaust manifold. The 96/97/98 318/360 Jeep Grand Cherokee exhaust ports are the same as the 340 exhaust ports.....no difference. The only smaller exhaust ports are the early 273/318 engine heads. treblig
                 
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                • ed1946

                  ed1946 FABO Gold Member FABO Gold Member

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                  I will ck when I get ready to work on motor
                   
                • bobscuda67

                  bobscuda67 Well-Known Member

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                  The Magnum port is shorter in height than the 340 LA port and will leak out of the bottom. I had to make adapters to go from Magnum heads to the 340 exhaust manifolds.
                  Check out post 14.
                   
                • ed1946

                  ed1946 FABO Gold Member FABO Gold Member

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                  So what do adapters look like? I really don't have any equipment to make adapters. How about putting the 2 different gaskets, 340 and magnum, together behind 340 manifolds.
                   
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                  • toolmanmike

                    toolmanmike FABO Staff Staff Member FABO Gold Member

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                    Next time please start a wanted thread. Thanks
                     
                  • DionR

                    DionR Well-Known Member

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                    My adapters are just 14 or 16 gauge plates with the inside shape matching the inside of the Magnum exhaust gasket, and the outside matching the 340 manifold. Then I sandwiched them between a Magnum gasket on the head side and a 340 gasket on the other side.

                    In my case, they have been a little problematic, too. I expect that at some point I will just spring for a set of Doug's headers and get rid of them. I had to re-gasket them once and the second time around they didn't seal well. Could have been something I did wrong, or could be they don't want to seal more than once.

                    I have pictures of them installed, but I don't think I have any after I got them cut on a plasma table here at work.

                    P8170487.JPG P8170489.JPG

                    Here is a screenshot of the AutoCAD file I used to get them cut. Started with a scan of both gaskets and traced what I needed and merged them together.

                    Capture.PNG
                     
                  • ed1946

                    ed1946 FABO Gold Member FABO Gold Member

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                    ok, thanks
                     
                  • bobscuda67

                    bobscuda67 Well-Known Member

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                    That's what mine ended up looking like. Except I made mine by hand out of 16 gauge flat stock.
                    They have been on the engine for 9 years and no leaks.
                     
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