MPG Motor Magnum vs. Hemi

Magnum Engine Swaps

  1. oldkimmer

    oldkimmer FABO Gold Member FABO Gold Member

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    Just thinking out loud, can u bolt the 518 od tranny to a 5.7 Hemi, then u will have the best combination for fuel mileage. Is there a 4barrel intake for the Hemi? Kim
     
  2. slicknapier

    slicknapier Well-Known Member

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    Yes the 518 will bolt to the Hemi with the correct flex plate. Yes ther is a 4 barrel manifold for the Hemi, but that would defeat the purpose of the Hemi swap. It would definitely be injected.
     
  3. sccachallenger

    sccachallenger Well-Known Member

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    Sounds like you want the 5.7, I don't blame you!
    If the engine runs you $1500, that leaves $2500 from your budget.
    Have you added up?
    driveshaft, oil filter adapter,engine mounts,oil pan,exhaust mods,radiator,trans lines,shifter mods,electric or cable throttle pedal,wiring harness and computer mods, fuel pump and/or tank, flex plate and fasteners, A/C lines, power steering hoses, freon, coolant, ATF, oil.
    What am I leaving out?
    I hope you can do it for your budget.
     
  4. slicknapier

    slicknapier Well-Known Member

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    I’m not really biased one way or another. I just know that having my Magnum motor with fuel injection as my daily is awesome. I’m just trying to be realistic and weigh all my options. I know the small stuff adds up quickly.
    I pulled the valve cover off the 413 and found a bent pushrod. It had a stuck valve. We thought it was bent, but it turned out the valve was just rusty and hung up. Took a couple hours to free up the valve, but we got it moving smoothly. Straightened the push rod and threw it back together. The 413 purrs like a kitten now!! It is definitely smoking a lot less. I am going to finish doing all the umbrella seals and see how it does, hell maybe the 413 will be good to go? Thanks

    8E151E9B-A25A-4B26-A98E-C82EA8CA454F.jpeg
     
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    • oldkimmer

      oldkimmer FABO Gold Member FABO Gold Member

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      I would get a another push rod. It bent once, it will again. Kim
       
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      • slicknapier

        slicknapier Well-Known Member

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        Definitely will. Just ironing issues out. Trying to not spend to much money on it until I make a definitive plan..
         
      • dartfever

        dartfever FABO Gold Member FABO Gold Member

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        Could always use the A518 on the 413 with an adapter. adapters
         
      • MRGTX

        MRGTX Well-Known Member

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        It sounds like the discussion is evolving but I thought 273's post was an interesting point....and absolutely true. Doing the math on this one, especially with ~$3.00 hi-test gasoline, you'd have to drive A LOT of miles to pay for the mods with MPG improvements.

        That said, it OP is talking road trip...and in this case range is a big consideration. So I suspect that fuel cost isn't the only concern.

        As for the original question, I'd look at the cost of a Magnum with higher compression heads, custom cam and EFI compared to the 5.7 Hemi. It seems like this might tip the scales toward the Magnum.
         
      • slicknapier

        slicknapier Well-Known Member

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        I am leaning towards the magnum motor as of now. I think picking one oup around $500 or so then putting a little $$$ into it will get me where I need to be???Maybe!! Who knows..
         
      • MopaR&D

        MopaR&D Nerd Member FABO Gold Member

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        I think keeping the 413 and tuning it up really well (carb, ignition) should get highway mileage up into the high teens. Also going to larger wheels and tires will bump up your gearing a bit, 3.21 is just a hair on the short side for high-speed road tripping IMO. It's a tough call with the transmission though, personally I'm not a huge fan of the 518 I've heard they suck a ton of power and don't give the MPG improvements they should. Maybe a GM O/D trans or a Gear Vendors...?
         
      • slicknapier

        slicknapier Well-Known Member

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        Gear vendors pretty much throws away any idea of a budget. They are definitely awesome, but I could do a lot with the $$$ they cost..
         
      • Pascamp

        Pascamp Well-Known Member

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        You can find a good used 4l80e trans for @$500. New controllers are roughly $500, but used ones are plentiful for half that. Finding the adapter for a Mopar big block used would require a lot of luck. New ones are $500ish. So, for a little over a grand you can have the best trans ever built. Add a TBI set up for about a grand, and now you've got your wish. Modern reliability, probably 20mpg and way more power and torque than the Magnum. I think all the 413's we're pretty good HP wise.
         
      • slicknapier

        slicknapier Well-Known Member

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        Well I think I’m going to do the Magnum swap. I picked up free 2001 Ram that was wrecked. A tad over 200,000 miles, but the price was right. Looks like the trans was rebuilt,so that’s a step in the right direction. I am going to tear down the motor and rebuild it. Going to do EQ heads and figure out what cam will be my best option. I’ll probably do a tanks inc. mustang tank with the fuel pump in it and sink it in where the spare tire is supposed to go. Started working on the harness, so fingers crossed I can figure it out!

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      • mgoblue9798

        mgoblue9798 Active Member

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        You mentioned doing a previous retrofit and now are doing this one. How are you modifying the wiring harness to work? Do you have a diagram? Maybe you could make a few dollars from the rest of us drawing one up? I know I would be interested.
         
      • BigBlockMopar

        BigBlockMopar BigBlockMember

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        Where are you going to put the gastank?
        The wagon's stock tank is designed upright in the left rear fender. You'll have to sacrifice the rear 'basement' sparewheel area.

        Don't forget the transmission detent spring and lever has to changed/modified for the pushbutton gearselector to work properly.

        I also own a '62 Chrysler New Yorker wagon.
        It's my backup car in case the Dart is out of commission.
         
        Last edited: Jun 3, 2018
      • AJ/FormS

        AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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        5.2 Magnum
        Cheap, easy, modest compression, hi-torque beer barrel intake, stone age reliable,
        Easy to find, burns anything at cruise rpm, can be geared for low revs and still pulls with computer controlled mega-timing. Worry-free, relaxing sight-seeing family time.
         
        Last edited: Jun 3, 2018
      • slicknapier

        slicknapier Well-Known Member

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        Mgoblue, on my Crewcab I used the entire harness including the pdc, gauges, fuel tank etc...The wiring is to bulky for me and I have a lot of wires bundled up and just tied out of the way. It is my daily driver/business truck so I have to leave it alone for now. When I get done with this I will try to draw up a diagram. I feel no need to make any $$$ off anyone, but I will definitely share what I learn along the way.

        Bigblockmopar, my spare tire well is a little rusty on the wagon and will need to be cut out. My plan as of now is to cut it out and re-configure it to accommodate the mustang tank with a fuel injection pump. I’ve tried to find info about converting the push-buttons, but haven’t come up with anything definitive. If you have some info I am all ears. I would like to keep my factory fuel tank as well, might sound ridiculous, but here me out! I would like to put an electric fuel pump off the factory tank or somehow use the factory filler to fill both tanks. Just brainstorming on that one.
         
      • slicknapier

        slicknapier Well-Known Member

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      • BigBlockMopar

        BigBlockMopar BigBlockMember

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        You could connect the 2 tanks with a lower feed and upper vent line so you can use and fill them together at the same time.
        As the stock tank is upright and probably higher than your 2nd tank, it will always properly flow into the 2nd tank with the fuelpump.

        A guy running Imperial Services used to make/provide conversion cables to hook a later style transmission to stock pushbutton controls.
        One of the mods was to replace the detent spring with a weaker one, as the lever on the transmission is very short, because the throw of the pushbuttons is short too.

        There was speak of him not wanting to deal directly with buyers anymore so he might sell his items through a dealer. But I'm not sure if he still does this.
        His prices were very firm btw.
         
      • slicknapier

        slicknapier Well-Known Member

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        I have heard of imperial services, just never hear anything good about them.
         
      • pishta

        pishta I know I'm right....

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        Never met a magnum that got better than 10 mpg. No idea why these were so thirsty.
         
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        • slicknapier

          slicknapier Well-Known Member

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          Maybe it’s a driving style? The only time I really check mine is on road trips. I avg. about 13 mpg in my 63 Crewcab pulling a 1956 Shasta camp trailer. If you’re getting 10 mpg I would think something was very wrong?
           
        • robcuda

          robcuda FABO Gold Member FABO Gold Member

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          Regarding fuel tank, if you're going to cut up the back area for a tank you should consider making a space for a 15 gal aluminum fuel tank, $120, route the filler to it. You said you would like to use stock pump, cut a hole in the aluminum tank and place stock pump. A few guys have done this. You can even cut the collar from donor tank and bolt it to top of aluminum tank. Way more affordable thank tanks inc and plug and play with the fuel pump. I considered this route but for various reasons I could not.
           
        • mgoblue9798

          mgoblue9798 Active Member

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          Had a 92 dakota with a 318 magnum that averaged 18mpg. It would do low 20's on the highway.
           
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          • MopaR&D

            MopaR&D Nerd Member FABO Gold Member

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            Nice going with the Magnum swap, with the EFI you should definitely see some MPG improvements even including a cam and EQ heads (current route I'm going for with a 5.9L in my Duster but it'll be carb'd).

            @mgoblue9798 that was the 1st-gen Dak right? Those things are tiny compared to a '94-02 Ram, or an old C-body... would love to get my hands on one with a 5-speed. Or swap a 5.2L into my '93 XJ Cherokee lol.
             
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